tag:theconversation.com,2011:/au/topics/great-white-sharks-8564/articlesGreat white sharks – The Conversation2022-09-02T01:21:53Ztag:theconversation.com,2011:article/1648642022-09-02T01:21:53Z2022-09-02T01:21:53ZWho would win in a fight between a great white shark and a blue whale?<figure><img src="https://images.theconversation.com/files/482435/original/file-20220902-18-adneuh.png?ixlib=rb-1.1.0&rect=5%2C11%2C3988%2C1982&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock/The Conversation</span></span></figcaption></figure><p><em>This article is part of the “<a href="https://theconversation.com/au/topics/who-would-win-in-a-fight-103258">Who would win?</a>” series, where wildlife experts dream up hypothetical battles between predators (all in the name of science).</em></p>
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<p>One is the largest animal known to have ever existed. The other is a revered predator at the top of its food chain. But would a blue whale and a great white shark ever find themselves at odds with each other in the wild? </p>
<p>While such observations of sharks attacking whales are few, we know it does occur.
The scars many whales bear throughout their lives resulting from shark attacks are more than sufficient evidence sharks will have a go if an opportunity arises.</p>
<p>Their fight is about survival – a potentially much longed-for next meal for a shark, and the whale’s desperate defence to ensure the next generation’s survival. So, which of these impressive marine giants would win?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/482199/original/file-20220901-19649-4yglhc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/482199/original/file-20220901-19649-4yglhc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/482199/original/file-20220901-19649-4yglhc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/482199/original/file-20220901-19649-4yglhc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/482199/original/file-20220901-19649-4yglhc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/482199/original/file-20220901-19649-4yglhc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/482199/original/file-20220901-19649-4yglhc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/482199/original/file-20220901-19649-4yglhc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">White sharks have teeth designed to rip flesh.</span>
<span class="attribution"><span class="source">Marcelo Cidrack/Unsplash</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<h2>A grand banquet</h2>
<p>At up to 30 metres long and weighing over 100 tonnes, a blue whale easily outsizes a white shark, which can measure perhaps over 6m and weigh less than a tonne.</p>
<p>But the blue whale didn’t get so big from killing and eating other large animals such as sharks. Rather, they evolved an efficient way of consuming very large amounts of tiny prey: krill. </p>
<p><a href="https://journals.biologists.com/jeb/article/214/1/131/10226/Mechanics-hydrodynamics-and-energetics-of-blue">They lunge</a> through dense patches of thousands, if not millions, of krill, with large, gaping jaws that can open up to around 80 degrees. </p>
<p>The lunge builds enormous water pressure against their mouth, inflating the pleat-like grooved blubber around their mouth cavity to balloon like an accordion’s bellows. With this remarkable device, blue whales can engulf thousands of litres of water in one go. </p>
<p><a href="https://theconversation.com/curious-kids-why-dont-whales-have-teeth-like-we-do-186727">Instead of teeth</a>, blue whales (along with humpbacks, and many other whale species) have bristle-like baleen, which strain the small organisms from the water when their mouth cavity is compressed. This is how blue whales maximise their energy intake while minimising effort.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/cbxSBDopVyw?wmode=transparent&start=3" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A blue whale lunging for krill | National Geographic.</span></figcaption>
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<p>Sharks, on the other hand, are highly specialised apex predators that hunt and capture large animals, such as large fish, seals and sea lions, and sometimes even dolphins.</p>
<p>They are well designed for this, with streamlined bodies designed for ambush-and-chase style hunting. They also have flexible and extensible jaws and sharp teeth designed to grab and rip flesh.</p>
<p>If a shark could successfully capture a large whale, the winnings would be one of a grand banquet. After all, what better meal than the massive source of high energy of the meat and thick, fatty blubber a whale brings! </p>
<p>Indeed, <a href="https://www.abc.net.au/news/2022-05-16/shark-feeding-frenzy-drone-footage-albany-fisher-wa/101069876">media reports</a> often capture images of sharks lurking around large whale carcasses. </p>
<p>So, have these carcasses resulted from shark predation? Or have these whales died from an otherwise unknown ailment, or human impacts such as fishing gear entanglement?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/482198/original/file-20220901-22-vll3w5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/482198/original/file-20220901-22-vll3w5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/482198/original/file-20220901-22-vll3w5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/482198/original/file-20220901-22-vll3w5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/482198/original/file-20220901-22-vll3w5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/482198/original/file-20220901-22-vll3w5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/482198/original/file-20220901-22-vll3w5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/482198/original/file-20220901-22-vll3w5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A white shark taking a bite out of a dead whale.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<h2>A formidable defender</h2>
<p>Large sharks are not only hunters, but also scavengers. <a href="https://www.sciencedirect.com/science/article/pii/S2351989419301854">Growing evidence</a> suggests whale carcasses are an important part of the diets of large sharks. In fact, the fat in whale blubber can significantly increase a shark’s metabolism.</p>
<p>With whale meat and blubber an important food for sharks, why might they not also hunt whales while they’re alive? It turns out whales can indeed become a large and highspeed target.</p>
<p>Blue whales’ highly streamlined bodies, however, have evolved to travel as fast as 40 kilometres per hour, for as much as an hour or more. Their speed and endurance make them difficult prey to catch for sharks. </p>
<p>Sharks employ more of a sit and wait strategy to conserve energy, and pursue prey over short, fast bursts of speed of up to at least <a href="https://www.tandfonline.com/doi/full/10.1080/17451000.2011.614255">11 metres per second</a>. </p>
<p>But the difficulties for a shark in capturing a blue whale don’t end with their limited endurance at high speed. Unless you’re a large shark, say, over several meters long, you simply may not have sufficient power in your jaws to effectively tear off the meat, even if you could keep up with a blue whale.</p>
<p>Some <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2907.2008.00118.x">other baleen whales</a>, such as southern right whales that can reach over 16m-long, are less streamlined than blue whales due to their chunkier, but more flexible, bodies. For them, a fight rather than flight defence strategy against predators may be taken.</p>
<p>To defend against killer whales, for example, such whales have been reported to <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2907.2008.00118.x">group together</a> and defend themselves with powerful tail, pectoral fin or head blows at their attackers.</p>
<p>Right whales have also been <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2907.2008.00118.x">observed</a> taking these strong stances to protect their vulnerable calves. A well-calculated and well-timed tail slap or body slam may be life threatening to a predator.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/8KCQrLA3UKw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Orcas attack a blue whale, and the blue whale flees | National Geographic.</span></figcaption>
</figure>
<p>But when do the advantages of the predator defence mechanisms that whales have evolved start to wane? The answer is: when the odds are stacked against them. </p>
<p>When a whale is vulnerable – perhaps it’s no older than a few weeks or months, or perhaps it’s unwell or otherwise compromised – it doesn’t have the same speed and defences of a healthy adult whale. </p>
<h2>So which species would win?</h2>
<p>As true for all things, it is situational. A whale threatened by a white shark could cause damage to its attacker. A blue whale also has the added advantage of high-speed endurance to flee if it prefers. </p>
<p>But if the whale is already vulnerable – such as a worn-out and debilitated whale entangled in fishing nets – then persistent and well-calculated attacks that cause the whale to bleed out can result in the shark winning and whale losing. </p>
<p>There was an interesting case off Massachusetts Bay in the United States in July 2015, when this almost certain destiny was reversed. The brave Marine Animal Entanglement Response team managed to free a <a href="https://coastalstudies.org/entangled-humpback-freed-from-entanglement-and-white-shark-interaction/">severely entangled humpback whale</a> that had sustained injuries from a 5m white shark. </p>
<p>The fact the entanglement made the whale vulnerable leaves food for thought on our own role in putting many whales at greater, unnatural risk of death – including many in endangered populations already struggling under human pressures. </p>
<p>I take this story as testament to the compassionate nature of humanity. But it’s also a sobering reminder of the urgent need for us to transition our current harmful practices to ones that are sustainable.</p><img src="https://counter.theconversation.com/content/164864/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chandra Salgado Kent receives funding fromt the National Environmental Science Program and the Australian Research Council for whale research.</span></em></p>The scars many whales bear throughout their lives resulting from shark attacks are more than sufficient evidence sharks will have a go if an opportunity arises.Chandra Salgado Kent, Associate Professor, School of Science, Edith Cowan UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1869312022-07-13T14:00:11Z2022-07-13T14:00:11ZKiller whales are hunting great white sharks in South Africa’s waters<figure><img src="https://images.theconversation.com/files/473862/original/file-20220713-20-peajvi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">shutterstock</span> </figcaption></figure><p>Great white sharks have long been at the top of the food chain in parts of South Africa’s oceans. In their peak winter hunting months, around 100 great white sharks a day could be observed off the coast of the Western Cape province. But in 2017, great white shark carcasses began to wash up on beaches at Gansbaai, one of the main sites where the species usually gathered. Some were <a href="https://www.tandfonline.com/doi/abs/10.2989/1814232X.2022.2066723#:%7E:text=Research%20Papers-,Fear%20at%20the%20top%3A%20killer%20whale%20predation%20drives%20white%20shark,South%20Africa's%20largest%20aggregation%20site&text=Risk%2Dinduced%20fear%20effects%20exerted,on%20ecosystem%20structure%20and%20function.">missing their livers</a>. And the numbers of great white sharks in Gansbaai <a href="https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecs2.2531">started to drop</a>. In fact, they just vanished for up to a year at a time. What was the cause?</p>
<p>The culprits appear to be a pair of male killer whales, which researchers have named Port and Starboard, that arrived in the area. They have a signature way of tearing open their prey and they favour the nutrient-rich liver. </p>
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<a href="https://images.theconversation.com/files/473907/original/file-20220713-9316-cprrjv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two killer whales in water" src="https://images.theconversation.com/files/473907/original/file-20220713-9316-cprrjv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473907/original/file-20220713-9316-cprrjv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=373&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473907/original/file-20220713-9316-cprrjv.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=373&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473907/original/file-20220713-9316-cprrjv.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=373&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473907/original/file-20220713-9316-cprrjv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=469&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473907/original/file-20220713-9316-cprrjv.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=469&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473907/original/file-20220713-9316-cprrjv.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=469&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Port and Starboard.</span>
<span class="attribution"><span class="source">David Hurwitz</span></span>
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<p>Though killer whales are known to hunt sharks far from shore elsewhere in the world, this was the first time the carcasses had washed up on a beach and become available for scientific study.</p>
<p>In today’s episode of Pasha, shark biologist and PhD candidate Alison Towner tells the unfolding story of the impact the killer whales are having on South Africa’s marine ecosystems. Great white sharks are fleeing to other parts of the coast and their absence affects other species like African penguins and Cape fur <a href="https://www.nature.com/articles/s41598-019-39356-2">seals</a>.</p>
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<a href="https://images.theconversation.com/files/473861/original/file-20220713-24-zifvc4.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Great white shark dead on beach as people surround it." src="https://images.theconversation.com/files/473861/original/file-20220713-24-zifvc4.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473861/original/file-20220713-24-zifvc4.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=288&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473861/original/file-20220713-24-zifvc4.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=288&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473861/original/file-20220713-24-zifvc4.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=288&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473861/original/file-20220713-24-zifvc4.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=362&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473861/original/file-20220713-24-zifvc4.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=362&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473861/original/file-20220713-24-zifvc4.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=362&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="attribution"><span class="source">Tami Kaschke, Dyer Island Conservation Trust</span></span>
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<p>It’s a novel situation, with concerns for the <a href="https://www.dffe.gov.za/sites/default/files/reports/sharksconservationmanagement_nationaplanofaction_review2020october.pdf">tourism</a> and <a href="https://dict.org.za/">conservation</a> sectors – and no simple answers.</p>
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<p><strong>Photo</strong>
“Great white shark” by Mogens Trolle, found on <a href="https://www.shutterstock.com/image-photo/great-white-shark-south-africa-132857996">Shutterstock</a>.</p>
<p><strong>Music</strong>
“Happy African Village” by John Bartmann, found on <a href="http://freemusicarchive.org/music/John_Bartmann/Public_Domain_Soundtrack_Music_Album_One/happy-african-village">FreeMusicArchive.org</a> licensed under <a href="https://creativecommons.org/publicdomain/zero/1.0/">CC0 1</a>.</p>
<p>“African Moon” by John Bartmann, found on <a href="http://freemusicarchive.org/music/John_Bartmann/Public_Domain_Soundtrack_Music_Album_One/happy-african-village">FreeMusicArchive.org</a> licensed under <a href="https://creativecommons.org/publicdomain/zero/1.0/">CC0 1</a>.</p>
<p><strong>Sounds</strong>
“orcas (killer whales)” by MBARI_MARS found on <a href="https://freesound.org/people/MBARI_MARS/sounds/458854/">Freesound</a> licensed under <a href="http://creativecommons.org/licenses/by-nc/3.0/">attribution noncommercial 3.0 license</a>.</p><img src="https://counter.theconversation.com/content/186931/count.gif" alt="The Conversation" width="1" height="1" />
A pair of killer whales are hunting and preying on South Africa's great white sharks, forcing the sharks to flee.Ozayr Patel, Digital EditorLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1828412022-06-20T12:29:50Z2022-06-20T12:29:50ZMillions of years ago, the megalodon ruled the oceans – why did it disappear?<figure><img src="https://images.theconversation.com/files/466658/original/file-20220601-48845-thu3o5.jpg?ixlib=rb-1.1.0&rect=35%2C0%2C4000%2C2694&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Roaming the ancient seas eons ago, the megalodon shark eviscerated its prey with jaws that were 10 feet wide.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/megalodon-scene-3d-illustration-royalty-free-image/1004792742?adppopup=true">Warpaintcobra/iStock via Getty Images Plus</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
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<blockquote>
<p><strong>When did the megalodon shark go extinct, and why? – Landon, age 10</strong></p>
</blockquote>
<hr>
<p>Imagine traveling back in time and observing the oceans of 5 million years ago. </p>
<p>As you stand on an ancient shoreline, you see several small whales in the distance, gliding along the surface of an ancient sea.</p>
<p>Suddenly, and without warning, an enormous creature erupts out of the depths. </p>
<p>With its massive jaws, the monster crushes one of the whales and drags it down into the deep. Large chunks of the body are ripped off and swallowed whole. The rest of the whales scatter.</p>
<p>You have just witnessed mealtime for megalodon – formally known as <em><a href="https://www.howtopronounce.com/otodus-megalodon">Otodus megalodon</a></em> – the largest shark ever. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/466672/original/file-20220601-48323-58vfyy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="In one hand rests an enormous tooth from a megalodon; in the other hand, two teeth from a great white shark. The megalodon tooth is about six times as large as those of the great white." src="https://images.theconversation.com/files/466672/original/file-20220601-48323-58vfyy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/466672/original/file-20220601-48323-58vfyy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/466672/original/file-20220601-48323-58vfyy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/466672/original/file-20220601-48323-58vfyy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/466672/original/file-20220601-48323-58vfyy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/466672/original/file-20220601-48323-58vfyy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/466672/original/file-20220601-48323-58vfyy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">At left, a megalodon tooth; at right, for comparison, two teeth from a great white shark.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/prehistoric-megalodon-shark-tooth-and-two-great-royalty-free-image/1294765101">Mark Kostich/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<h2>About the megalodon</h2>
<p><a href="https://case.fiu.edu/about/directory/profiles/heithaus-michael.html">As a scientist</a> who studies sharks and other ocean species, I am fascinated by the awesome marine predators that have appeared and disappeared through the eons. </p>
<p>That includes huge swimming reptiles like <a href="https://www.kidsnews.com.au/animals/britains-largest-ichthyosaur-skeleton-excavated-in-england/news-story/57f2dcf393250b16f27b75ccbb1ca1a2">ichthyosaurs</a>, <a href="https://theconversation.com/plesiosaurs-pliosaurs-hybodonts-looking-back-at-three-prehistoric-predators-of-the-jurassic-seas-174828">plesiosaurs</a> and the <a href="https://www.livescience.com/mosasaurus-mosasaur.html">mosasaurs</a>. These incredible predators lived during the time of the dinosaurs; megalodon would not appear for another 50 million years. </p>
<p>But when it did arrive on the scene, about 15 million to 20 million years ago, the megalodon must have been an incredible sight. </p>
<p>A fully grown individual weighed about 50 metric tons – that’s more than 110,000 pounds (50,000 kilograms) – and was 50 to 60 feet long (15 to 18 meters). This animal was longer than a school bus and as heavy as a railroad car!</p>
<p>Its jaws were up to 10 feet (3 meters) wide, the teeth up to 7 inches (17.8 centimeters) long and <a href="https://oceanconservancy.org/blog/2020/08/24/7-mega-wild-facts-megalodon/#:%7E:text=With%20a%20jaw%20estimated%20to,40%2C000%20pounds%20per%20square%20inch.">the bite force</a> was 40,000 pounds per square inch (2,800 kilograms per square centimeter). </p>
<p>Not surprisingly, megalodons ate big prey. Scientists know this because they’ve found chips of megalodon teeth embedded in the bones of large marine animals. On the menu, along with whales: large fish, seals, sea lions, dolphins and other sharks. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/466458/original/file-20220531-48845-gffx97.jpg?ixlib=rb-1.1.0&rect=44%2C53%2C5946%2C2937&q=45&auto=format&w=1000&fit=clip"><img alt="An artist's conception of a megalodon shark, with black eyes and a mouth wide open, chasing a pod of striped dolphins." src="https://images.theconversation.com/files/466458/original/file-20220531-48845-gffx97.jpg?ixlib=rb-1.1.0&rect=44%2C53%2C5946%2C2937&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/466458/original/file-20220531-48845-gffx97.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/466458/original/file-20220531-48845-gffx97.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/466458/original/file-20220531-48845-gffx97.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/466458/original/file-20220531-48845-gffx97.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/466458/original/file-20220531-48845-gffx97.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/466458/original/file-20220531-48845-gffx97.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An artist’s vision of what megalodon might have looked like. Megalodon was found in the warm ocean waters of the tropics and subtropics. Its teeth have been found on every continent except Antarctica.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/megalodon-attack-royalty-free-image/481819827">Corey Ford/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<h2>Are scientists sure megalodon is extinct?</h2>
<p>Internet rumors persist that modern-day megalodons exist – that they still swim around in today’s oceans. </p>
<p>But that’s not true. Megalodons are extinct. They died out about 3.5 million years ago. </p>
<p>And scientists know this because, once again, they looked at the teeth. All sharks – including megalodons – produce and ultimately lose tens of thousands of teeth throughout their lives.</p>
<p>That means lots of those lost megalodon teeth <a href="https://science.lovetoknow.com/understanding-science/explaining-fossils-kids">are around as fossils</a>. Some are found at the bottom of the ocean; others <a href="https://www.greatyarmouthmercury.co.uk/news/boy-finds-rare-megalon-tooth-bawdsey-beach-8940068">washed up on shore</a>. </p>
<p>But nobody has ever found a megalodon tooth that’s less than <a href="https://earthathome.org/quick-faqs/how-do-scientists-date-rocks-and-fossils/">3.5 million years old</a>. That’s one of the reasons scientists believe megalodon went extinct then.</p>
<p>What’s more, megalodons spent much of their time relatively close to shore, a place where they easily found prey. </p>
<p>So if megalodons still existed, people would certainly have seen them. They were way too big to miss; we would have lots of photographs and videos. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/BTPcq2HczVY?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Watch this PBS Eons video and learn more about the megalodon shark.</span></figcaption>
</figure>
<h2>Why megalodon disappeared</h2>
<p>It probably wasn’t one single thing that led to the extinction of this amazing megapredator, but a complex mix of challenges. </p>
<p>First, the climate dramatically changed. Global water temperature dropped; that reduced the area where megalodon, a warm-water shark, could thrive. </p>
<p>Second, because of the changing climate, entire species that megalodon preyed upon vanished forever. </p>
<p>At the same time, competitors helped push megalodon to extinction – that includes the <a href="https://www.livescience.com/27338-great-white-sharks.html">great white shark</a>. Even though they were only one-third the size of megalodons, the great whites probably ate some of the same prey. </p>
<p>Then there were <a href="https://www.earthtouchnews.com/discoveries/fossils/giant-killer-sperm-whales-once-cruised-australias-waters-and-we-have-a-massive-tooth-to-prove-it/">killer sperm whales</a>, a now-extinct type of sperm whale. They grew as large as megalodon and had even bigger teeth. They were also warmblooded; that meant they enjoyed an expanded habitat, because living in cold waters wasn’t a problem. </p>
<p>Killer sperm whales probably traveled in groups, so they had an advantage when encountering a megalodon, which probably hunted alone. </p>
<p>The cooling seas, the disappearance of prey and the competition – it was all too much for the megalodon. </p>
<p>And that’s why you’ll never find a modern-day megalodon tooth.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/rThDFJFaRow?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">From NatGeo Kids: What it’s like to be a marine biologist.</span></figcaption>
</figure>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/182841/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Heithaus does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A terrifying sight in ancient waters, the megalodon shark was once the most feared creature in the sea.Michael Heithaus, Executive Dean of the College of Arts, Sciences & Education and Professor of Biological Sciences, Florida International UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1841312022-06-06T14:59:52Z2022-06-06T14:59:52ZHow great white sharks outsmarted the massive megalodon to first rule the oceans, 3 million years ago<figure><img src="https://images.theconversation.com/files/466612/original/file-20220601-48284-ipylp2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">davidpstephens / shutterstock</span></span></figcaption></figure><p>When my children ask me, “What’s your favourite dinosaur?” I always respond, “A megalodon.” This is much to their disgust, as they expect the stock answer of Rexy or <a href="https://theconversation.com/evict-dippy-from-the-natural-history-museum-this-dinosaur-expert-says-go-for-it-36921">Dippy</a>. But as a shark enthusiast, I may need to change my answer and say great whites (and their ancestors) after scientists have showed the two species coexisted and competed – and it would appear the great whites won.</p>
<p>I wasn’t being entirely honest with my kids, who rightly point out that megalodon existed some time after the last dinosaurs died out (excluding birds). But it was nonetheless a true beast, the largest predator ever to inhabit our oceans, growing to a phenomenal size of 18 metres and weighing in at over 50 tonnes. For comparison, a great white can grow up to 6 metres but weighs less than 2 tonnes.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/466629/original/file-20220601-48284-ybzir0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram showing megalodon, great white shark and human to scale" src="https://images.theconversation.com/files/466629/original/file-20220601-48284-ybzir0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/466629/original/file-20220601-48284-ybzir0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=307&fit=crop&dpr=1 600w, https://images.theconversation.com/files/466629/original/file-20220601-48284-ybzir0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=307&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/466629/original/file-20220601-48284-ybzir0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=307&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/466629/original/file-20220601-48284-ybzir0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=385&fit=crop&dpr=1 754w, https://images.theconversation.com/files/466629/original/file-20220601-48284-ybzir0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=385&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/466629/original/file-20220601-48284-ybzir0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=385&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Don’t mess with megalodon.</span>
<span class="attribution"><span class="source">EreborMountain / shutterstock</span></span>
</figcaption>
</figure>
<p>Until recently, scientists largely believed that great white sharks were smaller, faster versions of megalodons. But in recent years, new evidence has moved us away from thinking they were members of the same family, and its genus is still debated among marine biologists. </p>
<p>Now the latest research suggests the two species existed at the same time and were in competition with one another. The new study, published in the journal <a href="https://www.nature.com/articles/s41467-022-30528-9">Nature Communications</a>, has raised the question whether the great white was among the potential causes of the megalodon’s extinction.</p>
<h2>Only the teeth remain</h2>
<p>Until recently, the abrupt disappearance in the fossil record of the megalodon 2.5 million years ago remained a mystery. To investigate what happened, the researchers behind the new study decided to look at the diet of great white sharks, their ancestors and megalodon.</p>
<p>One of the problems with researching sharks is that their skeletons are mostly made of cartilage, so after decomposition almost all that remains are teeth. Learning about these animals from fossil evidence therefore requires a best-guest approach based on species that roam the earth today. What we know about megalodon is based almost entirely on their teeth (megalodon even means “big tooth”) and scientists have to make educated guesses about the rest of their bodies.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/466620/original/file-20220601-48861-8b00pd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="man stands beside large fossilised jaw" src="https://images.theconversation.com/files/466620/original/file-20220601-48861-8b00pd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/466620/original/file-20220601-48861-8b00pd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=572&fit=crop&dpr=1 600w, https://images.theconversation.com/files/466620/original/file-20220601-48861-8b00pd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=572&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/466620/original/file-20220601-48861-8b00pd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=572&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/466620/original/file-20220601-48861-8b00pd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=718&fit=crop&dpr=1 754w, https://images.theconversation.com/files/466620/original/file-20220601-48861-8b00pd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=718&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/466620/original/file-20220601-48861-8b00pd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=718&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Man vs megalodon.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/jsjgeology/15336195195/">James St. John / flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>So how do you investigate the diet of a long-gone animal, when only its teeth have survived? To solve this problem, scientists looked for concentrations of zinc isotopes in the fossilised teeth of megalodon and in teeth of past and present great whites. </p>
<p>Isotopes are variants of an element that act as a sort of chemical signature. In this case, different zinc isotopes can indicate what sort of diet a fossilised animal had and where it sat in the food chain. </p>
<p>The presence of the same levels of different zinc isotopes suggested that great white ancestors and megalodons once ate the same food and occupied the same position in the food web. There then appears to have been a shift as the great whites – the newcomers, the underdogs – relegated megalodon and took over.</p>
<h2>Changing climate, changing sharks</h2>
<p>How could the demise of the largest ever apex predator have coincided with the rise of one of today’s apex predators? One theory that aligns with the analysis in the latest research is that a changing climate is responsible. During the dominance of megalodon, the climate was milder and the seas were generally warmer, enabling the large predator to patrol all over both the northern and southern hemispheres. </p>
<p>The rise of great white sharks coincided with with changing sea conditions and general cooling at both poles. Cooler waters meant krill boomed in coastal areas, as did the baleen whales that fed on them. As megalodon was only able to survive in warmer waters, the more adaptable great whites were able to exploit the absence of a key competitor and feast on the growing whale populations. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/466628/original/file-20220601-48537-aoqtmx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Movie poster" src="https://images.theconversation.com/files/466628/original/file-20220601-48537-aoqtmx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/466628/original/file-20220601-48537-aoqtmx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=851&fit=crop&dpr=1 600w, https://images.theconversation.com/files/466628/original/file-20220601-48537-aoqtmx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=851&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/466628/original/file-20220601-48537-aoqtmx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=851&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/466628/original/file-20220601-48537-aoqtmx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1069&fit=crop&dpr=1 754w, https://images.theconversation.com/files/466628/original/file-20220601-48537-aoqtmx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1069&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/466628/original/file-20220601-48537-aoqtmx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1069&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Megalodon is depicted as the ultimate predator, but got outsmarted by a more adaptable rival.</span>
<span class="attribution"><a class="source" href="https://www.imdb.com/title/tt15295912/">Megalodon Rising (2021) / imdb</a></span>
</figcaption>
</figure>
<p>Colleagues and I research the environmental factors affecting great white sharks in <a href="https://link.springer.com/article/10.1007/s10641-021-01094-8">Mossel Bay, South Africa</a>, and it is fairly well known that the present-day species exist in water temperatures ranging from 12°C to 24°C. At the lower end, this would have been too cold for the megalodon. It appears that, as whales and other marine mammals adapted to cooler climes a few million years ago, great whites followed them into these waters and were able to sit at the top of the food chain. The megalodons would have had to settle for smaller fish in warmer waters, with less of the high-energy fatty blubber they needed. </p>
<p>Great white sharks appear to have benefited from the “survival of the fittest”. People often confuse this Darwinian phrase as meaning the strongest and biggest survive. But it really revolves around which species is best adapted to survive the changes in the environment and come out the other side alive, able to carry on the lineage and reproductive success of the species.</p><img src="https://counter.theconversation.com/content/184131/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicholas Ray does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>As the oceans warmed, great whites were more adaptable.Nicholas Ray, Doctoral School Programmes Manager, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1804782022-04-11T12:14:43Z2022-04-11T12:14:43ZGreat white sharks occasionally hunt in pairs – new research sheds light on social behavior of these mysterious predators<figure><img src="https://images.theconversation.com/files/457187/original/file-20220408-20-xvfjtz.JPG?ixlib=rb-1.1.0&rect=38%2C240%2C3178%2C2484&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Great white sharks are not normally thought of as social creatures.</span> <span class="attribution"><span class="source">Yannis Papastamatiou</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Sitting anchored to the rocky reef 70 feet (21 meters) below the surface of the ocean, hundreds of scalloped hammerhead sharks swam above me in unison, moving as if one. When most people think of sharks, they don’t think of them as social creatures. The schooling hammerhead sharks above my head were a striking example of shark social groups, a topic that has not been the subject of much exploration.</p>
<p>I am <a href="https://scholar.google.com/citations?user=qudaP1wAAAAJ&hl=en&oi=ao">a marine biologist</a> and <a href="https://www.peclabfiu.com/">study the behavior of predators</a>. For the last 22 years, my research has focused on sharks.</p>
<p>Biologists have long known that some sharks – like hammerheads – are social creatures, but whether great white sharks interact with each other while hunting, and if so, how, is still a mystery. Since 2014, my colleagues and I have visited the beautiful Guadalupe Island off the coast of Mexico to try to find out. Using state of the art technology, we have been able to gain a better understanding of the secret social lives of these top predators.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/4BdjxYUdJS8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Some creatures, like ants, form highly complex social systems based around cooperation, but there are many levels of social behavior.</span></figcaption>
</figure>
<h2>What makes a social animal?</h2>
<p>A social animal is one that interacts and spends time with other individuals of the same species. While nearly all animals show some degree of sociality – when they mate, for example – social behaviors can range from <a href="https://doi.org/10.1016/B978-0-12-802213-9.00002-X">solitary snow leopards</a> to <a href="https://doi.org/10.1111/j.1558-5646.1996.tb04492.x">highly social ant colonies</a>.</p>
<p>When people think of social predators, most probably picture a pack of wolves hunting in an organized, cooperative group. But social behavior can be much simpler than that. An animal may simply decide to stay in close proximity to another individual because it has learned that if its “colleague” locates some prey, <a href="https://doi.org/10.1038/s41559-017-0245-0">its own chances of getting a meal increase</a>. </p>
<p>The sharing of information – the location of prey – in this example is inadvertent. The first predator wasn’t purposefully alerting the second predator to the presence of a meal. But under the right conditions, this type of basic social interaction can <a href="https://doi.org/10.1371/journal.pcbi.1005147">increase the success of both animals’ hunting</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/457186/original/file-20220408-21-fnnh0j.JPG?ixlib=rb-1.1.0&rect=76%2C267%2C3435%2C2402&q=45&auto=format&w=1000&fit=clip"><img alt="A shark in the ocean." src="https://images.theconversation.com/files/457186/original/file-20220408-21-fnnh0j.JPG?ixlib=rb-1.1.0&rect=76%2C267%2C3435%2C2402&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457186/original/file-20220408-21-fnnh0j.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457186/original/file-20220408-21-fnnh0j.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457186/original/file-20220408-21-fnnh0j.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457186/original/file-20220408-21-fnnh0j.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457186/original/file-20220408-21-fnnh0j.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457186/original/file-20220408-21-fnnh0j.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Great white sharks were historically seen as individualistic hunters, but previous research hinted at social behaviors.</span>
<span class="attribution"><span class="source">Yannis Papastamatiou</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Hints of a social shark</h2>
<p>White sharks travel to seal colonies <a href="https://doi.org/10.3354/meps07628">during the seal’s breeding seasons</a> in the summer and fall. Sharks generally hunt by patrolling the waters adjacent to seal colonies and ambush seals at the surface. </p>
<p>In 2001, researchers in California published a paper describing how white sharks patrolling a seal colony at Año Nuevo Island would <a href="https://doi.org/10.1007/s002270000489">remain within “eavesdropping” distance of each other</a>. The biologists suggested that if one shark killed a marine mammal, other, nearby sharks would register this information and quickly approach the site of the kill, perhaps hoping to eat from the remains of the prey. While the sharks may not be cooperating, they can still potentially benefit by hanging out with each other.</p>
<p>Further studies on white shark behavior in Australia took this a step further. Researchers found that white sharks would often turn up at <a href="https://doi.org/10.1007/s00265-019-2745-1">cage diving sites with the same individuals</a> time and time again. The fact that white sharks not only stay close to each other but also have preferred buddies got me wondering if maybe these animals were more social than people thought.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/457191/original/file-20220408-42486-1pet9o.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photo of a large island from the sea with clouds spilling over." src="https://images.theconversation.com/files/457191/original/file-20220408-42486-1pet9o.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457191/original/file-20220408-42486-1pet9o.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457191/original/file-20220408-42486-1pet9o.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457191/original/file-20220408-42486-1pet9o.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457191/original/file-20220408-42486-1pet9o.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457191/original/file-20220408-42486-1pet9o.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457191/original/file-20220408-42486-1pet9o.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Guadalupe Island off the northwestern coast of Mexico is home to a number of seal colonies, and great white sharks are regular visitors in fall and winter.</span>
<span class="attribution"><span class="source">Yannis Papastamatiou</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>How to tag a great white shark</h2>
<p>Guadalupe Island is located about 150 miles (240 km) west of Mexico’s Baja Peninsula. Every fall, at least <a href="https://doi.org/10.1038/s41598-020-74294-4">100 white sharks arrive at the island to feed</a> on Guadalupe fur seals, California sea lions, squid and tuna. In 2014, I reached out to my friend and colleague, <a href="https://www.pelagioskakunja.org/dr-mauricio-hoyos">Mauricio Hoyos-Padilla</a>, who has been tagging white sharks at Guadalupe for over 15 years, to see if he was interested in studying white shark social behavior. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/457189/original/file-20220408-25011-u2csvc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A large, yellow rectangular piece of technology." src="https://images.theconversation.com/files/457189/original/file-20220408-25011-u2csvc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/457189/original/file-20220408-25011-u2csvc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=452&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457189/original/file-20220408-25011-u2csvc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=452&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457189/original/file-20220408-25011-u2csvc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=452&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457189/original/file-20220408-25011-u2csvc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=568&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457189/original/file-20220408-25011-u2csvc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=568&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457189/original/file-20220408-25011-u2csvc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=568&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The social tag can detect nearby sharks with transmitters, allowing researchers to see when sharks were near each other.</span>
<span class="attribution"><span class="source">Yannis Papastamatiou</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>To do this, we developed a new electronic tag that we call the “social tag.” It has sensors that can detect simple acoustic transmitters that we attached to other sharks, allowing us to see which sharks hang out with each other and for how long. The social tags also include a video camera and motion sensors that can track how fast the shark is swimming and how deep it is.</p>
<p>Starting in 2017, I would head to Guadalupe every year for about a week to try to tag sharks with Mauricio and his students from the nonprofit research organization <a href="https://www.pelagioskakunja.org">Pelagios-Kakunja</a>. Sometimes we would tag sharks from the safety of cages, but more often we would free dive with them. We would use bait to attract a shark to the boat and when one appeared, three or four taggers would jump into the crystal clear water. We would then wait for one of these large sharks to get curious and swim within a few feet of us. When that happened, we would use a long pole to clamp the tag onto the dorsal fin of the shark.</p>
<p>Over three years of successful tagging, we deployed our social tags on three male and three female sharks and tagged another 37 individuals with acoustic transmitters. The tags would stay on for one to five days before falling off and floating to the surface for the team to recover. In total, we collected over 312 hours of data from the six social tags.</p>
<h2>When sharks hang out</h2>
<p>Over the many hours of data that we collected, the sharks frequently came within 100 feet (30 meters) of other individuals. Many of these meetings were short and seemingly random – kind of like crossing paths with someone at a grocery store – but a few lasted longer and appeared to be true social interactions. We recorded five instances of these longer interactions, one of which lasted for over an hour. </p>
<p>We also found that individual sharks behaved quite differently from one another. Two of the tagged sharks were particularly social and associated with 12 and 16 other individuals, while two others appeared much less social, only crossing paths with only four and six other sharks respectively. The tags used on the final two sharks did not have working sensors on them, so we were not able to measure interactions.</p>
<p>Another interesting behavioral difference was that some sharks hunted in shallow waters and others hunted hundreds of meters deep.</p>
<p>Our new evidence suggests that white sharks are indeed social animals. Just as previous research suggested, our results fit with the idea that that the benefit of white shark sociality is that they can “eavesdrop” on other sharks. They can quickly acquire information such as a seal killed at depth by another shark, and this could end leading to an easy meal. However, there is so much more to learn. </p>
<p>Measuring sociality over months and over a year, as opposed to just days, would provide much deeper insights. When the sharks leave Guadalupe Island in the spring, they travel long distances across the open ocean – some swim as far as Hawaii. Do they travel together or by themselves? </p>
<p>The social lives of white sharks have been a secret hidden from researchers for decades. It took new technology and new research methods to see it.</p><img src="https://counter.theconversation.com/content/180478/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Yannis Papastamatiou receives funding from Sharkproject International and Great White Mystery. </span></em></p>Researchers have discovered that great white sharks are more social than previously thought. Using specialized tags, they tracked six sharks and found that some stay close to each other when hunting.Yannis Papastamatiou, Professor of Biological Sciences, Florida International UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1714402021-11-09T22:13:19Z2021-11-09T22:13:19ZWhite sharks can easily mistake swimmers or surfers for seals. Our research aims to reduce the risk<figure><img src="https://images.theconversation.com/files/430964/original/file-20211109-21-fpdq3d.jpeg?ixlib=rb-1.1.0&rect=9%2C199%2C3010%2C2064&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Great_White_Shark_(14730796397).jpg">Elias Levy/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>The <a href="https://www.abc.net.au/news/2021-11-07/search-continues-for-shark-bite-victim-port-beach/100601006">presumed death of 57-year-old Paul Millachip</a> in an apparently fatal shark bite incident near Perth on November 6 is a traumatising reminder that while shark bites are rare, they can have tragic consequences. </p>
<p>Despite the understandably huge media attention these incidents generate, there has been little scientific insight into how and why they happen.</p>
<p>Sharks in general, and white sharks in particular, have long been described as “<a href="https://www.news-press.com/story/news/2015/05/14/great-whites-mindless-killing-machines/27313547/">mindless killers</a>” and “<a href="https://www.walesonline.co.uk/news/uk-news/new-discovery-makes-man-eating-21484244">man-eaters</a>”.</p>
<p>But our <a href="https://royalsocietypublishing.org/doi/10.1098/rsif.2021.0533">recent research</a> confirms that some bites on humans may be the result of mistaken identity, whereby the sharks mistake humans for their natural prey based on visual similarities. </p>
<p>Sharks have an impressive array of senses, but vision is thought to be particularly important for prey detection in white sharks. For example, they can attack seal-shaped decoys at the surface of the water even though these decoys lack other sensory cues such as scent. </p>
<p>The visual world of a white shark varies substantially from that of our own. White sharks are likely colourblind and rely on brightness, essentially experiencing their world in shades of grey. Their eyesight is also much less acute than ours – in fact, it’s probably more akin to the blurry images a human would see underwater without a mask or goggles.</p>
<h2>The mistaken identity theory</h2>
<p>Bites on surfers have often been explained by the fact that, seen from underneath, a paddling surfer looks a lot like a seal. But this presumed similarity has only previously been assessed based on human vision, using underwater photographs to compare their silhouettes. </p>
<p>Recent developments in our understanding of sharks’ vision have now made it possible to examine the mistaken identity theory from the shark’s perspective, using a virtual system that generates “shark’s-eye” images.</p>
<p>In our study, <a href="https://royalsocietypublishing.org/doi/10.1098/rsif.2021.0533">published last month</a>, we and our colleagues in Australia, South Africa and the United Kingdom compared video footage of seals and of humans swimming and paddling surfboards, to predict what a young white shark sees when looking up from below. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/431041/original/file-20211109-15-746s0s.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Shark's-eye images of surfer and seal" src="https://images.theconversation.com/files/431041/original/file-20211109-15-746s0s.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/431041/original/file-20211109-15-746s0s.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=330&fit=crop&dpr=1 600w, https://images.theconversation.com/files/431041/original/file-20211109-15-746s0s.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=330&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/431041/original/file-20211109-15-746s0s.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=330&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/431041/original/file-20211109-15-746s0s.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=414&fit=crop&dpr=1 754w, https://images.theconversation.com/files/431041/original/file-20211109-15-746s0s.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=414&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/431041/original/file-20211109-15-746s0s.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=414&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">‘Shark’s-eye view’ of a paddling surfer and seal, suggesting white sharks may struggle to differentiate the two.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We specifically studied juvenile white sharks – between of 2m and 2.5m in length – because <a href="https://www.frontiersin.org/articles/10.3389/fmars.2020.00268/full#B6">data</a> from New South Wales <a href="https://www.hindawi.com/journals/jmb/2016/9539010/">suggests</a> they are more common in the surf zone and are disproportionately involved in bites on humans. This might be because juvenile sharks are more likely to make mistakes as they switch to hunting larger prey such as seals.</p>
<p>Our results showed it was impossible for the virtual visual system to distinguish swimming or paddling humans from seals. This suggests both activities pose a risk, and that the <a href="https://www.publish.csiro.au/mf/MF10181">greater occurrence of bites on surfers</a> might be linked to the times and locations of when and where people surf.</p>
<p>Our analysis suggests the “mistaken identity” theory is indeed plausible, from a visual perspective at least. But sharks can also detect prey using other sensory systems, such as smell, sound, touch and detection of electrical fields.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-do-shark-bites-seem-to-be-more-deadly-in-australia-than-elsewhere-85986">Why do shark bites seem to be more deadly in Australia than elsewhere?</a>
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<p>While it seems unlikely every bite on a human by a white shark is a case of mistaken identity, it is certainly a possibility in cases where the human is on the surface and the shark approaches from below.</p>
<p>However, the mistaken identity theory cannot explain all shark bites and other factors, such as curiosity, hunger or aggression are likely to also explains some shark bites.</p>
<h2>Can this knowledge help protect us?</h2>
<p>As summer arrives and COVID restrictions lift, more Australians will head to the beach over the coming months, increasing the chances they might come into close proximity with a shark. Often, people may not even realise a shark is close by. But the past weekend gave us a reminder that shark encounters can also tragically result in serious injury or death. </p>
<p>Understanding why shark bites happen is a good first step towards helping reduce the risk. Our research has inspired the design of non-invasive, vision-based shark mitigation devices that are currently being tested, and which change the shape of the silhouette.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/fatal-shark-attacks-are-at-a-record-high-deterrent-devices-can-help-but-some-may-be-nothing-but-snake-oil-150845">Fatal shark attacks are at a record high. 'Deterrent' devices can help, but some may be nothing but snake oil</a>
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<p>We still have a lot to learn about how sharks experience their world, and therefore what measures will most effectively reduce the risks of a shark bite. There is a plethora of devices being developed or commercially available, but only a few of them have been scientifically tested, and even fewer – such as the devices made by <a href="https://ocean-guardian.com.au/">Ocean Guardian</a> that create an electrical field to ward off sharks – have been <a href="https://peerj.com/articles/5554/">found</a> to genuinely reduce the risk of being bitten.</p><img src="https://counter.theconversation.com/content/171440/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Laura Ryan receives funding from State and Federal government agencies and non-governmental organisations. </span></em></p><p class="fine-print"><em><span>Charlie Huveneers receives funding from State and Federal government agencies, private donors, and non-governmental organisations. </span></em></p>The death of 57-year-old Paul Millachip at Fremantle’s Port Beach is a reminder that shark bites, though rare, can be tragic. New research aims to reduce the risk by understanding sharks’ vision.Laura Ryan, Postdoctoral Researcher, Department of Biological Sciences, Macquarie UniversityCharlie Huveneers, Associate professor, Flinders UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1541022021-01-27T16:36:28Z2021-01-27T16:36:28ZOceanic sharks and rays have declined by 71% since 1970 – a global solution is needed<figure><img src="https://images.theconversation.com/files/380907/original/file-20210127-19-gu3qgz.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4353%2C2893&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/manta-ray-241545559">Rich Carey/Shutterstock</a></span></figcaption></figure><p>Oceanic sharks and rays live so far from land that the average person is unlikely to ever see them. But these species, which live in the vast open ocean, are also among the most revered, and include the great white shark and the giant manta ray. For millennia, their remoteness has allowed these species to largely avoid humans. But since the early 1950s, industrial-scale fishing fleets have been able to reach distant waters and gradually spread to exploit the entire global ocean. </p>
<p>Rising demand over the same period for shark and ray meat, as well as fins, gill plates and liver oil, has caused catches of the 30 or so oceanic species to soar. Marine biologists have been raising the alarm for several decades now, but their warnings were often limited to what regional trends showed. Now, <a href="https://www.nature.com/articles/s41586-020-03173-9">new research</a> has brought together disparate threads of data into a single, global analysis of shark and ray populations in the open ocean.</p>
<p>Worldwide, oceanic shark and ray abundance has declined by 71% since 1970. More than half of the 31 species examined are now considered to be endangered, or even critically endangered. Compare this with 1980 when only one species, the plankton-feeding basking shark, was thought to be endangered. These are stark statistics, and they indicate that the future for the ocean’s top predators is fast deteriorating.</p>
<h2>Nose dive</h2>
<p>To arrive at the first global perspective on oceanic shark and ray population trends, the study synthesised a huge amount of data. The researchers calculated two separate indicators of biodiversity, using indexes established by the Convention on Biological Diversity to track progress towards international targets. They used state-of-the-art modelling to estimate trends in the relative abundance of species. One of the indicators combined assessments of 31 species by the <a href="https://www.iucnredlist.org/">IUCN Red List</a> over a 38-year period.</p>
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<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><strong><em>This story is part of <a href="https://theconversation.com/uk/topics/oceans-21-96784">Oceans 21</a></em></strong>
<br><em>Our series on the global ocean opened with <a href="https://oceans21.netlify.app/">five in-depth profiles</a>. Look out for new articles on the state of our oceans in the lead up to the UN’s next climate conference, COP26. The series is brought to you by The Conversation’s international network.</em></p>
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<p>The results revealed huge declines in the abundance of sharks in the Atlantic, Indian and Pacific oceans. Once abundant species such as the oceanic whitetip shark have declined by 75% globally in just the past half-century, while populations of the endangered shortfin mako shark – valued for its meat and fins – have shrunk by about 40%. Manta ray populations have suffered even greater losses.</p>
<p>The study attributes these declines to overfishing. The researchers documented a greater than twofold increase in fishing pressure from longline fisheries for instance, which use lines stretching 100km and bearing 1,200 baited hooks. These lines are deployed each day by any one of the thousands of longlining vessels worldwide, snaring sharks in the open ocean either intentionally or as bycatch while targeting other marine life.</p>
<figure class="align-center ">
<img alt="A slab with several dead sharks lying on it." src="https://images.theconversation.com/files/380903/original/file-20210127-21-bfpx38.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1597%2C1200&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/380903/original/file-20210127-21-bfpx38.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/380903/original/file-20210127-21-bfpx38.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/380903/original/file-20210127-21-bfpx38.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/380903/original/file-20210127-21-bfpx38.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/380903/original/file-20210127-21-bfpx38.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/380903/original/file-20210127-21-bfpx38.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Shortfin mako sharks are one of the world’s fastest animals, but often fall foul of fishing gear.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Shortfin_mako_shark#/media/File:Poxa_de_marraxo_(Isurus_oxyrinchus)_no_porto_pesqueiro_de_Vigo.jpg">José Antonio Gil Martínez</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The study also found increases in the proportion of sharks that are being fished beyond sustainable levels. But it’s particularly worrying that unreported catches weren’t included in the study’s analyses. This means the number of sharks and rays killed by fishing boats is likely to be an underestimate and the actual declines of these species may be even worse. Unlike most species of bony fish, sharks and rays produce few offspring and grow slowly. The rate at which they reproduce is clearly no match for current levels of industrialised fishing.</p>
<h2>Regulating the high seas</h2>
<p>Immediate and far-reaching action is needed to rebuild these populations. It’s clear that the rate of overfishing has outstripped the implementation of fisheries management measures and trade regulations. Since most oceanic sharks and rays are caught in the high seas – areas beyond national jurisdictions – agreements between fishing nations within management organisations are needed for conservation measures to work. </p>
<p>But, as this new study details, fishery limits imposed by management organisations of regional tuna fisheries – bodies tasked with managing oceanic sharks and ray populations – have been largely inadequate in following scientific advice. As recently as November 2020, the EU and US blocked a catch retention ban for North Atlantic shortfin mako sharks, despite <a href="https://science.sciencemag.org/content/371/6527/355">scientific evidence</a> clearly indicating that it was the first rung on a ladder to restoring this population of an endangered species.</p>
<figure class="align-center ">
<img alt="Several hooks gathered together in a line." src="https://images.theconversation.com/files/380910/original/file-20210127-17-16s18rt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/380910/original/file-20210127-17-16s18rt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/380910/original/file-20210127-17-16s18rt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/380910/original/file-20210127-17-16s18rt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/380910/original/file-20210127-17-16s18rt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/380910/original/file-20210127-17-16s18rt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/380910/original/file-20210127-17-16s18rt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Longline fishing deploys several hooks at once.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/longline-fishing-on-lofoten-islands-norway-1098959816">Lunghammer/Shutterstock</a></span>
</figcaption>
</figure>
<p>To begin the recovery of oceanic shark and ray populations, strict measures to prohibit landings of these species and to minimise their bycatch in other fisheries are needed immediately. This must be coupled with strict enforcement. Reducing the number of sharks and rays caught accidentally will be crucial but challenging, especially for longline fishing, which is not very selective and inadvertently catches lots of different species. This currently means that bans on intentional fishing are unlikely to be effective on their own. One solution would include modifying fishing gear and improving how fishers release sharks and rays after capture, to give them a better chance of survival.</p>
<p>An equally important measure, noted in the current study, would be banning fishing fleets from hotspots of oceanic sharks and rays. <a href="https://doi.org/10.1038/s41586-019-1444-4">Research published in 2019</a> highlighted where these areas in the global ocean overlap with fishing vessels most. Led by the UN, negotiations are underway for a high seas treaty which would create no-take marine reserves to protect threatened species in the open ocean. This new study should urge the international community to take such action while there’s still time.</p><img src="https://counter.theconversation.com/content/154102/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Sims has received funding from NERC, ERC and the Save Our Seas Foundation. He is an elected member of Academia Europaea, a fellow of the Zoological Society of London, a professional member of the Marine Biological Association of the UK, a life member of the Royal Institution of Great Britain, and a council member of the Fisheries Society of the British Isles.</span></em></p>A high seas treaty could help rebuild populations – but time is running out.David Sims, Professor of Marine Ecology, University of SouthamptonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1508452020-11-30T05:09:16Z2020-11-30T05:09:16ZFatal shark attacks are at a record high. ‘Deterrent’ devices can help, but some may be nothing but snake oil<figure><img src="https://images.theconversation.com/files/371871/original/file-20201130-15-1ejab8y.jpg?ixlib=rb-1.1.0&rect=22%2C0%2C2992%2C2002&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>As summer descends, sharks may be at the forefront of the minds of many beach goers and reef adventurers.</p>
<p>Globally, the number of shark bites is <a href="https://research.bond.edu.au/en/publications/unprovoked-shark-bites-are-they-becoming-more-prevalent">on the rise</a>, with a threefold increase since 1982. White sharks, bull sharks and tiger sharks are most commonly responsible. </p>
<p>In Australia this year, there have been 20 unprovoked shark bites (when humans don’t initiate contact) — a similar number to <a href="https://taronga.org.au/conservation-and-science/australian-shark-attack-file#viewthereportstatistics">recent years</a>. However, we’ve had eight fatalities, the highest on record since 1929. The latest fatality was at <a href="https://www.abc.net.au/news/2020-11-24/shark-warnings-before-broome-attack/12912226">Cable Beach</a> in Western Australia, a location not recognised as a shark bite hotspot.</p>
<p>Still, the risk of an unprovoked shark bite is still exceptionally low. You’re <a href="https://research.bond.edu.au/en/publications/unprovoked-shark-bites-are-they-becoming-more-prevalent">more likely</a> to drown at a beach than be killed by a shark. But there are things people can do to reduce the already low risk even further.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/371872/original/file-20201130-13-tu2io8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Aerial shot of Cable Beach" src="https://images.theconversation.com/files/371872/original/file-20201130-13-tu2io8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/371872/original/file-20201130-13-tu2io8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/371872/original/file-20201130-13-tu2io8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/371872/original/file-20201130-13-tu2io8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/371872/original/file-20201130-13-tu2io8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/371872/original/file-20201130-13-tu2io8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/371872/original/file-20201130-13-tu2io8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Last week a 59-year-old man was killed by a shark in Cable Beach in Broome, the first fatal shark incident in almost 30 years.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>What’s behind the shark bite trends?</h2>
<p>There is no single reason for the observed trends in unprovoked shark bite. </p>
<p><a href="https://www.sciencedirect.com/science/article/abs/pii/S0964569116302058">A 2016 study</a> found more people in the water contributes to rising incidents, as populations around coastal cities and towns increase. But this doesn’t tell the whole story.</p>
<p>Another reason may be due to <a href="https://www.sciencedirect.com/science/article/abs/pii/S0964569116302058">changes in the distribution</a> and an increasing abundance of key prey such as humpback whales (<em>Megaptera novaeangliae</em>) and New Zealand fur seal (<em>Arctocephalus forsteri</em>) along parts of the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3941575/">coast</a>. </p>
<p>For some sharks, weather conditions can also play a role. This is the case for bull sharks, which are commonly found in warm, shallow waters along coasts and rivers, such as in <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0146911">Sydney Harbour</a> during summer and autumn when water temperatures are higher.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/371875/original/file-20201130-18-1ll7gka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Bull shark swims near smaller fish" src="https://images.theconversation.com/files/371875/original/file-20201130-18-1ll7gka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/371875/original/file-20201130-18-1ll7gka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/371875/original/file-20201130-18-1ll7gka.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/371875/original/file-20201130-18-1ll7gka.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/371875/original/file-20201130-18-1ll7gka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/371875/original/file-20201130-18-1ll7gka.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/371875/original/file-20201130-18-1ll7gka.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Bull sharks are more active after heavy rainfall, especially near river mouths.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>After flooding, there is a heightened risk of an unprovoked bite, as bull sharks prefer <a href="https://www.tandfonline.com/doi/abs/10.2989/02577619109504636">turbid water</a> in the coastal zone. In other words, more rain generally means more bull shark activity. </p>
<p><a href="https://www.sciencedirect.com/science/article/pii/S2351989418302476">Research in 2018</a> confirmed this. The authors found when total rainfall in a catchment near a beach was greater than or equal to 100 millimetres, the bull shark catch increased between one and eight days later. </p>
<p>And as we’re entering a summer with <a href="https://theconversation.com/la-nina-will-give-us-a-wet-summer-thats-great-weather-for-mozzies-147180">La Niña weather conditions</a> — which means we’ll see increased rainfall — the risk of encountering a bull shark will be higher, particularly near river mouths.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/la-nina-will-give-us-a-wet-summer-thats-great-weather-for-mozzies-147180">La Niña will give us a wet summer. That's great weather for mozzies</a>
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</em>
</p>
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<h2>Shark deterrent technology</h2>
<p>If you want to learn about safety and sharks, it’s a good idea to start at the Shark Smart websites for <a href="https://www.daf.qld.gov.au/sharksmart">Queensland</a> and <a href="https://www.sharksmart.nsw.gov.au/">NSW</a>, which provide simple ways to reduce your personal risk. </p>
<p>This includes identifying times, locations and conditions to avoid, such as not swimming at dawn and dusk, and avoiding swimming with schools of baitfish or diving birds. </p>
<p>For those wanting greater peace of mind, personal electric shark deterrents are commercially available, with products suitable for divers, surfers and swimmers.</p>
<p>Sharks have a set of sense organs called <a href="https://theconversation.com/the-shocking-facts-revealed-how-sharks-and-other-animals-evolved-electroreception-to-find-their-prey-91066">ampullae of Lorenzini</a> that <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/1749-4877.12095">can detect</a> very weak electric currents in the water. Deterrent devices produce a electric current strong enough to elicit an avoidance response by the sharks without hurting them. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-shocking-facts-revealed-how-sharks-and-other-animals-evolved-electroreception-to-find-their-prey-91066">The shocking facts revealed: how sharks and other animals evolved electroreception to find their prey</a>
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<p>No shark deterrent is 100% effective, but independent testing has demonstrated several can significantly reduce the risk of a bite. Still, results are variable. </p>
<p>For white sharks, one electric deterrent reduced the percentage of bait taken from <a href="http://www.hwctf.org/Huveneers%20C%20et%20al%202018%20Effectiveness%20of%20five%20personal%20shark%20bite%20deterrents%20for%20surfers.pdf">96% to 40%</a>. And for bull sharks, <a href="https://www.nature.com/articles/s41598-020-74799-y?fbclid=IwAR2S_cT7i4LwzjsoM95qjPyZb7hbTrOfLQIoV1vbugZkDHs25VxFuw2KPXo">researchers</a> tested several different electric deterrents and found the best-performing device resulted in a 42.3% reduction in baits being consumed.</p>
<p>Electric devices aren’t the only type of deterrent. Chemical deterrents based on a necromone (dead shark smell!) have been <a href="https://www.sciencedirect.com/science/article/pii/S0964569113000161?casa_token=MQfFPYIv88wAAAAA:mb2yHpL5fIUkNF-F7XO2EZciUxOpjqXARkOY938RbVwhG0KUVq2ynhmaPt80jvUONUdMgtqyQDF4">effectively</a> tested on Caribbean reef and blacknose sharks. They may not be effective against large species, such as tiger or white sharks though.</p>
<p>And research from earlier <a href="https://www.mdpi.com/1996-1944/13/22/5065">this year</a> on reinforced neoprene wetsuits — fortified with composite fibres — shows promise for reducing the physical trauma of a shark bite, potentially reducing the chance of a fatality or serious injury. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/NRyK6bA0-0U?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The Freedom+ Surf is an electric shark deterrent that has been independently tested.</span></figcaption>
</figure>
<h2>Know your deterrent from snake oil</h2>
<p>If you’re thinking of buying a deterrent, a challenge for consumers is that many on the market have little to no biological or ecological basis, and have not been independently tested, as CHOICE, Australia’s leading consumer advocacy group, <a href="https://www.choice.com.au/health-and-body/diet-and-fitness/surfing-and-snowboarding/articles/shark-repellents-review">pointed out in 2016</a>. </p>
<p>A shark deterrent is a safety device and as such should be the subject of an Australian Standard – similar to the way a life jacket must follow a standard – to ensure claims are valid. Currently no specific Australian Standard exists for shark deterrents.</p>
<p>No one can legally make a seat belt in their garage and sell it as an effective safety device. The same should apply to shark deterrents. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-do-shark-bites-seem-to-be-more-deadly-in-australia-than-elsewhere-85986">Why do shark bites seem to be more deadly in Australia than elsewhere?</a>
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<p>There is a risk a person may place themselves in a more dangerous situation than they otherwise would have on the false belief the deterrent they have purchased has some level of effectiveness.</p>
<p>If you are looking to purchase a shark deterrent, look for those that have been independently tested in the field and found to have an actual deterrent effect. Don’t just rely on anecdotes and “the vibe”. In any case, the most effective deterrent is to make informed choices when entering the water this summer.</p>
<p>And we should never lose sight that an unprovoked shark attack is traumatic for surviving victims, first responders, and friends and families who lose a loved one. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-will-sharks-respond-to-climate-change-it-might-depend-on-where-they-grew-up-150460">How will sharks respond to climate change? It might depend on where they grew up</a>
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</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/150845/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Daryl McPhee has previously received funding from the WA, NSW and Queensland governments to investigate unprovoked shark bite. </span></em></p>You’re more likely to drown at a beach than be killed by a shark. But there are things people can do to reduce the already low risk even further.Daryl McPhee, Associate Professor of Environmental Science, Bond UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/764502018-02-26T19:14:28Z2018-02-26T19:14:28ZFactFile: the facts on shark bites and shark numbers<figure><img src="https://images.theconversation.com/files/207813/original/file-20180226-140181-un3yf6.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6281%2C4045&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The CSIRO has provided new estimates of population sizes for White Sharks in Australian waters.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/great-white-shark-underwater-gansbaai-187721633">Fiona Ayerst/Shutterstock</a></span></figcaption></figure><p>Are there more sharks in Australian waters than there used to be, and are interactions between humans and shark increasing? Some Australian politicians <a href="https://thewest.com.au/news/sharks/esperance-shark-attack-fisheries-minister-dave-kelly-says-no-drum-lines-deployed-in-esperance-ng-b88449006z">have</a> <a href="https://www.perthnow.com.au/news/wa/frydenberg-says-blind-freddy-could-see-there-are-more-sharks-ng-2880626e17e34e8def6a7c983dfe6523">claimed</a> that to be the case.</p>
<p>Let’s look at the research.</p>
<p>The most reputable source for shark incident data in Australia is the <a href="https://taronga.org.au/conservation/conservation-science-research/australian-shark-attack-file">Australian Shark Attack file</a>, which is collated at Sydney’s Taronga Zoo. </p>
<p>The map below, created by The Conversation using data from the Australian Shark Attack File, shows incidents between sharks and humans in Australia between 1997 and 2017.</p>
<p>You can use the filter buttons in the map to explore the data by year, season, the type of injury, the type of shark involved, the type of incident – or a combination of all the filters. Press the ‘show all’ button to reset the search. </p>
<p><iframe id="tc-infographic-243" class="tc-infographic" height="400px" src="https://cdn.theconversation.com/infographics/243/f87e27e72eb6545d5422e204b9894dedaad0f92f/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>The number of recorded encounters between sharks and humans in Australia increased modestly between 1997 and 2017, but the reason for this is unclear. Over those two decades, the Australian population <a href="http://www.abs.gov.au/ausstats/abs@.nsf/featurearticlesbytitle/ADF9B2B905D43653CA256FCE001101B5?OpenDocument">increased</a> <a href="http://www.abs.gov.au/ausstats/abs@.nsf/Latestproducts/3101.0Main%20Features1Jun%202017?opendocument&tabname=Summary&prodno=3101.0&issue=Jun%202017&num=&view=">by 33%</a>, but that alone doesn’t explain the increase in recorded shark encounters.</p>
<p>Correcting for the growth in human population in Australia, the data show that between 1997 and 2017: </p>
<ul>
<li>incidents resulting in injury increased by 1.59%</li>
<li>incidents without injury increased by 0.36%, and </li>
<li>fatalities increased by 0.07%. </li>
</ul>
<p>Encounters between humans and sharks are extremely variable over time, and difficult to predict. The increases in recorded incidents between 1997 and 2017 are relatively small, and may be explained by factors not related to shark populations – such as increases in the reporting of shark encounters, or increasing beach use.</p>
<p><iframe id="tc-infographic-159" class="tc-infographic" height="900" src="https://cdn.theconversation.com/infographics/159/62c30e6dedecffbbeb4e059c8ab0e573d756f61b/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
<h2>Are there more sharks off the Australian coast?</h2>
<p>White Sharks (formerly Great White Sharks) are recorded as being responsible for 28 of the 36 fatal shark encounters in Australian waters between 1997 and 2017, and are the primary target of shark mitigation strategies of the Western Australian, New South Wales and Queensland governments.</p>
<p>So, has there been an increase in the number of White Sharks in Australian waters? </p>
<p>Estimating population numbers in the marine environment is difficult, especially for long-lived migratory species like White Sharks.</p>
<p>However, there is no evidence that White Sharks numbers are on the rise, either in Western Australia or along the Eastern coast. Despite targeted conservation efforts, the available research show stable or slightly declining numbers in these populations.</p>
<p>There are <a href="http://era.daf.qld.gov.au/id/eprint/4509/">two distinct populations</a> of White Sharks off Australian coasts – one to the west, and another to the east of Bass Strait, which separates Tasmania from mainland Australia. The eastern population includes New Zealand White Sharks.</p>
<p><a href="https://www.nespmarine.edu.au/document/national-assessment-status-white-sharks">Recent work</a> by the CSIRO through the National Environmental Science Program’s Marine Biodiversity Hub using innovative DNA analysis has provided us with the most detailed and reliable estimates of population size we have for this species.</p>
<p>The CSIRO study shows there has been a slight decline in <em>adult</em> White Shark populations since the year 2000. </p>
<p>Current adult abundance for the eastern Australasian population is estimated at 750, with an uncertainty range of 470 to 1,030. The southern-western adult population is roughly double the size, estimated at 1,460, with an uncertainty range of 760 to 2,250.</p>
<p>Including the available information about juvenile White Sharks, estimates of total size for the <em>eastern</em> population in 2017 was 5,460, with an uncertainty range of 2,909 to 12,802.</p>
<p>It’s difficult to detect population trends with White Sharks because of the length of time it takes juveniles to reach maturity – <a href="https://www.nature.com/articles/s41598-018-20593-w">around 15 years</a>. As protection of White Sharks <a href="http://www.environment.gov.au/marine/marine-species/sharks/whiteshark">began in the late 1990s</a>, any changes in abundance would only be starting to appear in current populations.</p>
<h2>How else can we measure White Shark populations?</h2>
<p>The traditional way of measuring shark and fish populations is by examining catches in commercial fisheries over long time periods. By correcting for the level of fishing effort – which is done by looking at things like the number of nets, hooks and tows deployed by fishermen – scientists can assume that changes in the “catchability” of sharks is related to their abundance.</p>
<p>But due to the relative rarity of catches of White Sharks by fishing vessels, this approach is less reliable for this species than the more recent genetic studies conducted by the CSIRO and outlined above.</p>
<p>Western Australia has a detailed measure of White Shark numbers assessed by catch data. A <a href="http://www.fish.wa.gov.au/Documents/research_reports/frr277.pdf">report published by the Western Australian Department of Fisheries in 2016</a> attempted to model changes in the southern-western Australian White Shark population since the late 1930s. The authors outlined four different plausible scenarios, none of which suggested a continuous increase in the number of White Sharks.</p>
<p>In New South Wales, there has been a <a href="https://theconversation.com/shields-and-smart-buoys-new-technology-to-protect-sharks-and-people-48577">cluster of shark bites in recent years</a>. Data from the <a href="http://www.dpi.nsw.gov.au/fishing/sharks/management/shark-meshing-bather-protection-program">NSW Shark Meshing (Bather Protection) Program</a>, managed by the NSW Department of Primary Industries, show a recent increase in White Sharks caught in nets placed near ocean beaches.</p>
<p>But when it comes to thinking about shark populations, we should not assume that these two facts are related. It’s important to remember that just because two things may correlate, it doesn’t mean that one caused the other. </p>
<p>These patterns could mean that the animals are coming closer to shore, rather than a population increase (or decrease).</p>
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<p><iframe id="Zzcem" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/Zzcem/2/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
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<h2>Shark and human interactions: what factors are at play?</h2>
<p>A <a href="http://www.sciencedirect.com/science/article/pii/S0964569116302058">2016 paper</a> examined six global shark bite “hotspots” – the United States, South Africa, Australia, Brazil, Reunion Island and the Bahamas – and concluded that when it comes to encounters between sharks and humans, there are a range of causes at play. </p>
<p>These include: </p>
<ul>
<li>rises in human population</li>
<li>habitat destruction/modification</li>
<li>changes in water quality</li>
<li>climate change</li>
<li>changing weather patterns, and </li>
<li>the distribution/abundance of prey.</li>
</ul>
<p>The authors also noted that shark encounters appear to happen in clusters. For example, 2009 saw a spike in shark encounters off the New South Wales coast. This coincided with an increase in beach attendance and beach rescues during what was an unusually warm summer for south-east Australia.</p>
<p>A <a href="http://www.publish.csiro.au/mf/MF10181">2011 paper</a> highlighted the popularity of water sports as a factor contributing to increased human-shark encounters. More people are taking part in water sports, and improvements in wetsuit technology mean that people are in the water for longer throughout the year.</p>
<p>However, there is limited information on the number of people who use Australian beaches, so this explanation needs to be further studied.</p>
<p>It’s vital that any strategies put in place to reduce the number of unprovoked encounters between humans and sharks in Australian waters are carefully considered, and based on the best available research.</p><img src="https://counter.theconversation.com/content/76450/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jane Williamson has received money from the Australian Research Council and from NSW Department of Primary Industries. She is Deputy Chair of the NSW Fisheries Scientific Committee</span></em></p><p class="fine-print"><em><span>Vincent Raoult has received funding from the NSW Department of Primary Industries and the University of Newcastle. </span></em></p>How many shark encounters have there been at your local beach? Explore our interactive map to see 20 years of incidents between humans and sharks in coastal waters around Australia.Jane Williamson, Associate Professor in Marine Ecology, Macquarie UniversityVincent Raoult, Postdoctoral fellow, University of NewcastleLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/914792018-02-08T10:02:51Z2018-02-08T10:02:51ZWorld-first genetic analysis reveals Aussie white shark numbers<figure><img src="https://images.theconversation.com/files/205456/original/file-20180208-180829-spy0i6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Estimating shark numbers is extremely difficult and very contentious.</span> <span class="attribution"><span class="source">Elias Levy/Flickr</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Of all apex predators, the white shark <em>Carchardon carcharias</em> (commonly known as the great white) is perhaps the most fascinating. The <a href="https://theconversation.com/why-do-shark-bites-seem-to-be-more-deadly-in-australia-than-elsewhere-85986">potential danger</a> from (<a href="https://theconversation.com/worried-about-shark-attacks-or-terrorism-heres-how-to-think-about-the-real-risk-of-rare-events-74690">very rare</a>) human interaction has embedded the species in our national consciousness. </p>
<p>Debate as to the size and status of the white shark populations across the globe is both vigorous and often contested, and it is fair to say we have never had an accurate picture. Now, for the first time we estimate that the total number of adult sharks across the Australasian region is around 2,210. We’re lacking data on juvenile sharks in one region so it’s difficult to say what the total Australasian population is, but it’s likely to be in excess of 8,000-10,000 animals.</p>
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Read more:
<a href="https://theconversation.com/worried-about-shark-attacks-or-terrorism-heres-how-to-think-about-the-real-risk-of-rare-events-74690">Worried about shark attacks or terrorism? Here's how to think about the real risk of rare events</a>
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<p>CSIRO researchers working with Australian and New Zealand scientists in the <a href="http://www.environment.gov.au/science/nesp">National Environmental Science Program</a> have used world-first <a href="http://www.environment.gov.au/science/nesp">genetic analysis</a> to investigate white shark populations. The results of this project, published on Thursday in the journal <a href="https://www.nature.com/articles/s41598-018-20593-w">Scientific Reports</a>, are the first estimates of white shark adult population size, trend and survival rates for the Australasian region.</p>
<h2>One fish, two fish…</h2>
<p>The widely used aphorism in marine and particularly fisheries modelling is that counting fish is like counting trees, but you can’t see them and they move around all the time. </p>
<p>Until now, researchers have had to rely on patchy sources, like historical catch data. The various shark control programs do not provide usable data on relative density over time. We do have information on white shark migration and population structure from <a href="https://blog.csiro.au/7000km-and-counting-on-the-tail-of-a-great-white-shark/">electronic tagging</a> and previous genetic studies, but these don’t tell us about shark numbers. </p>
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Read more:
<a href="https://theconversation.com/why-do-shark-bites-seem-to-be-more-deadly-in-australia-than-elsewhere-85986">Why do shark bites seem to be more deadly in Australia than elsewhere?</a>
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<p>To address this key problem we worked with colleagues across Australia and New Zealand to use a highly novel method called close-kin mark-recapture, first developed by CSIRO in the late 2000s to monitor <a href="https://www.nature.com/articles/ncomms13162">southern bluefin tuna</a>.</p>
<p>Close-kin mark-recapture first involves taking a tissue sample from a shark, alive or dead, obtaining a genetic profile of the animal, and than comparing it to all the other sharks and asking: are these sharks related, and if so how are they related?</p>
<p>Due to a number of factors, it is easier to take genetic samples from juvenile white sharks (in the 3.5 to 4m or less range) than from adults. </p>
<p>In the first phase, we compared the genetic data from juvenile white sharks to look for half-sibling pairs – animals who shared either a mother or a father. The half-siblings are the close-kin side of the problem. The chances of finding these pairs in the samples is determined by (a) the size of the adult population, and (b) the survival rate of adult sharks. </p>
<p>Higher numbers of sharks, or sharks with low survival rates, make it less likely to find siblings in the samples. </p>
<p>This linkage between a specific type of relatedness (half brothers or sisters) and the size and survival rate of the adult population is the mark-recapture side of the equation. In traditional wildlife tagging studies, we “mark” an animal in some way (physically or in terms of visual or genetic ID) and try to “recapture” it again sometime in the future. </p>
<p>The mark-recapture principle is exactly the same with this method. The key difference is that a juvenile shark carries the “mark” of its parent within its DNA, which is “recaptured” when you find a half-sibling pair. Find enough of these half-siblings, and you can estimate both adult numbers and survival rates.</p>
<h2>Population</h2>
<p>Currently, we believe there are two main populations of white shark in the Australasian region: the “Eastern” population, which is basically everything to the east of Bass Strait (including New Zealand), and the “Southern-Western” population, which appears to range from west of Bass Strait, around the South Australia and West Australia coasts as far north as Ningaloo Reef.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/205448/original/file-20180208-180829-bszlg5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/205448/original/file-20180208-180829-bszlg5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/205448/original/file-20180208-180829-bszlg5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/205448/original/file-20180208-180829-bszlg5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/205448/original/file-20180208-180829-bszlg5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/205448/original/file-20180208-180829-bszlg5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/205448/original/file-20180208-180829-bszlg5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/205448/original/file-20180208-180829-bszlg5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption"></span>
<span class="attribution"><span class="source">CSIRO</span>, <span class="license">Author provided</span></span>
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<p>As part of phase one of the project we looked for half-siblings among 75 Eastern Australasian juvenile sharks and found 20. To give this some context, 75 samples permits 2,775 unique comparisons between animals. So less than 1% of those comparisons were siblings. We estimated that the number of adult sharks to be around 470 (with a range of 280-650), with at least 90% surviving from one year to the next. Given limited data there was no precise information on adult population trend. </p>
<p>The close-kin approach can only tell us about the adult population, however. To extend these estimates to total population size, we need to know something about the survival rate of juvenile sharks. Using data from around 70 juvenile sharks fitted with acoustic emitters, archived under Australia’s <a href="http://imos.org.au/">Integrated Marine Observing System</a>, we estimated that juvenile sharks had an annual survival rate of around 73%. </p>
<p>Combining these juvenile survival estimates with the adult abundance and survival information from the close-kin analyses we estimated there to be around 4,060 (and a range of 2,500-6,750) white sharks in the whole Eastern population.</p>
<p>After obtaining these results from the initial data, we moved onto phase two of the project. We collected and processed more samples to obtain both more data for the Eastern population, and enough samples and half-sibling matches to estimate the adult population size in the Southern-Western region. In the East we now have 214 juvenile samples, and found 73 half-siblings; in the Southern-Western case we now have 175 samples, and found 27 half-siblings. </p>
<p>The revised estimates of adult population size in the East were around 750 (with a range of 470-1,030) and annual survival probabilities of 93%. Revised estimates of total population size in the Eastern region were around 5,460 (with a range of 2,909-12,802). </p>
<p>Our initial estimates of the Southern-Western adult population were around 1,460 (with a range of 760-2,250) and that survival probabilities were very high (in the 90% and above range, as for the East). So these estimates suggest there are almost twice as many adult white sharks in the Southern-Western population relative to the East. </p>
<h2>Are shark populations increasing?</h2>
<p>In Australia white sharks have been protected under the <a href="http://www.environment.gov.au/epbc">Federal Environment Protection and Biodiversity Conservation Act</a> since 1999. Between 1995 and 1999 a national recovery plan was in effect. protected under various state legislation and subject to a national recovery plan. </p>
<p>We found that in both populations the adult population trend since protection has been essentially flat, with no evidence for a substantial increase or decrease. However, the picture is more uncertain when it comes to estimating population changes for younger white sharks. </p>
<p>White sharks take 12-15 years to mature. Assuming protection of the species reduced the juvenile mortality rate, then any such effect will not be apparent in the adult population until the next 5-10 years.</p>
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Read more:
<a href="https://theconversation.com/not-just-nets-how-to-stop-shark-attacks-without-killing-sharks-69400">Not just nets: how to stop shark attacks without killing sharks</a>
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<p>Balancing the conflicting goals of conservation and human protection is at times difficult and contentious. But, unquestionably, without being able to monitor populations effectively there is no way to resolve these questions. </p>
<p>Now we can monitor juveniles through electronic tagging programs, and keep track of adult populations with the close-kin method, we should finally have solved the problem of how to track the population size and status of this iconic predator.</p><img src="https://counter.theconversation.com/content/91479/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>New research has used genetic analysis in a world-first effort to accurately estimate Australian and New Zealand white shark numbers.Rich Hillary, Principal Research Scientist, CSIRORuss Bradford, Project leader and researcher, CSIROToby Patterson, Senior research scientist, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/859862017-11-01T01:57:59Z2017-11-01T01:57:59ZWhy do shark bites seem to be more deadly in Australia than elsewhere?<figure><img src="https://images.theconversation.com/files/192568/original/file-20171031-18735-19idlu0.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">White sharks' ability to stay warm in cold water makes them efficient long-range hunters.</span> <span class="attribution"><span class="source">Denice Askebrink</span></span></figcaption></figure><p>The first thing to say about shark attack deaths is that they are very rare, with only about <a href="https://taronga.org.au/conservation/conservation-science-research/australian-shark-attack-file">two per year in Australia</a>. But still, every year without fail, people die from shark bites, both here and around the world.</p>
<p>According to <a href="https://www.floridamuseum.ufl.edu/fish/isaf/shark-attacks-maps-data/trends/usa-highest-attacks/">official statistics</a>, the United States records by far the most unprovoked shark bites – an average of 45 per year over the past decade. However, only 1.3% of these incidents were fatal – 0.6 deaths per year. </p>
<p>Australia records fewer bites than the US (an average of 14 per year), but a much greater proportion of them are deadly: (1.5 per year, or close to 11%). So what is it that (relatively speaking) makes Australia more prone to deadly shark attacks?</p>
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Read more:
<a href="https://theconversation.com/not-just-nets-how-to-stop-shark-attacks-without-killing-sharks-69400">Not just nets: how to stop shark attacks without killing sharks</a>
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<p>My new book <a href="http://www.publish.csiro.au/book/7680/">Shark Attacks: Myths, Misunderstandings and Human Fear</a> addresses this and other questions about sharks, with the aim of dispelling common myths and providing the knowledge needed for decisions made on science rather than fear and emotion.</p>
<h2>A perfect storm</h2>
<p>In a way, Australia has a “perfect storm” of conditions for serious shark attacks. The first reason is that Australians (and visitors to Australia) love the ocean. Some 85% of Australians <a href="http://www.academia.edu/23432308/Being_beside_the_seaside_Beach_use_and_preferences_among_coastal_residents_of_south-eastern_Australia">live within 50km of the coast</a>, and Australian coastal areas account for the <a href="http://www.abs.gov.au/ausstats/abs@.nsf/Previousproducts/3218.0Main%20Features152014-15?opendocument&tabname=Summary&prodno=3218.0&issue=2014-15&num=&view=">most prominent growth outside of capital cities</a>. Beaches are also favoured recreational destinations in Australia and coastal locations are heavily targeted in tourism, attracting <a href="http://www.academia.edu/23432308/Being_beside_the_seaside_Beach_use_and_preferences_among_coastal_residents_of_south-eastern_Australia">nearly 60% of international tourists</a>.</p>
<p>Next, the sharks themselves. Australia has the world’s <a href="http://onlinelibrary.wiley.com/doi/10.1111/jfb.12874/abstract">highest diversity of sharks and rays</a>, including roughly 180 of the 509 known shark species. </p>
<p>But neither of these factors, even taken together, is enough to explain why deaths are more prevalent in Australia. What we really need to look at is dangerous sharks.</p>
<p>Only <a href="https://www.floridamuseum.ufl.edu/fish/isaf/contributing-factors/species-implicated-attacks/">26 shark species have been definitively identified as biting humans without provocation</a>, although the true number is likely to be somewhat higher. Of these 26 species, 22 (85%) are <a href="http://www.publish.csiro.au/book/5960/">found in Australian waters</a>. </p>
<p>All 11 of the species known to have caused fatal unprovoked bites on humans can be found in Australian waters. And crucially, Australia’s coastal waters are home to all of the “big three” deadly species: <a href="http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=64470">white sharks</a>, <a href="https://australianmuseum.net.au/tiger-shark-galeocerdo-cuvier-pron-lesueur-1822">tiger sharks</a>, and <a href="https://australianmuseum.net.au/bull-shark-carcharhinus-leucas-valenciennes-1839">bull sharks</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/192569/original/file-20171031-18693-1jucmmt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/192569/original/file-20171031-18693-1jucmmt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/192569/original/file-20171031-18693-1jucmmt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=351&fit=crop&dpr=1 600w, https://images.theconversation.com/files/192569/original/file-20171031-18693-1jucmmt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=351&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/192569/original/file-20171031-18693-1jucmmt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=351&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/192569/original/file-20171031-18693-1jucmmt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=442&fit=crop&dpr=1 754w, https://images.theconversation.com/files/192569/original/file-20171031-18693-1jucmmt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=442&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/192569/original/file-20171031-18693-1jucmmt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=442&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Australia’s waters are home to all three of the ‘big three’ shark species.</span>
<span class="attribution"><span class="source">Denice Askebrink</span></span>
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<p>These species account for all but three of the <a href="http://epublications.bond.edu.au/fsd_papers/42/">fatal shark attacks worldwide from 1982-2011</a>. All of the big three species are inquisitive, regularly frequent coastal environments, and are formidably big and strong. </p>
<p>They also have complex, unpredictable behaviour. But despite this difficulty, we can identify factors that make them more likely to swim in areas routinely used by humans.</p>
<h2>Warming to it</h2>
<p>White sharks have a physiological adaptation that allows them to maintain a vast global distribution, and hence are responsible for the <a href="http://www.sharkattackfile.net/incidentlog.htm">northernmost</a> and <a href="http://sharkattacksurvivors.com/shark_attack/viewtopic.php?t=1167">southernmost</a> recorded shark bites on humans.</p>
<p>Most fish are ectothermic, or cold-blooded, with body temperatures very close to that of the surrounding water. This restricts their range to places where the water temperature is optimal. </p>
<p>In contrast, white sharks and a few other related species can retain the heat generated by their muscles predominantly during swimming, enabling them to be swift and agile predators even in cold water. They do this with the help of <a href="https://link.springer.com/article/10.1023/A:1007650502269">bunches of parallel arteries and veins</a> in their brains, eyes, muscles and stomachs that function as “heat exchangers” between incoming and outgoing blood, allowing them to keep these crucial organs warm.</p>
<p>White sharks are so good at retaining heat that their core body temperature can be <a href="https://link.springer.com/article/10.1007%2Fs003600050092">up to 14.3°C above the surrounding water temperature</a>. This allows them to move seasonally up and down Australia’s east and west coasts, presumably <a href="https://link.springer.com/article/10.1007/s00227-006-0325-1">following migrating prey species</a>.</p>
<h2>Getting salty</h2>
<p>Bull sharks, meanwhile, are the only sharks known to <a href="https://www.ncbi.nlm.nih.gov/pubmed/14662294">withstand wide variations in water salinity</a>. This means they can easily move from salty oceans to brackish estuaries and even travel thousands of kilometres up river systems. As a result they can overlap with human use areas such as canals, estuaries, rivers and even some lakes. One female bull shark was observed making a <a href="http://onlinelibrary.wiley.com/doi/10.1111/jfb.12805/abstract">4,000km round-trip</a> to give birth in a secluded Madagascan estuary rather than the open ocean.</p>
<p>As a result, most bull sharks found in river systems are juveniles, but these areas may also be home to large, pregnant females who need to eat more prey to sustain themselves. As rivers are often clouded by sediment, there is an increased risk that a human may be mistaken for prey in this low-visibility environment.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/192769/original/file-20171101-13425-1tmjpcn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/192769/original/file-20171101-13425-1tmjpcn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/192769/original/file-20171101-13425-1tmjpcn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=432&fit=crop&dpr=1 600w, https://images.theconversation.com/files/192769/original/file-20171101-13425-1tmjpcn.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=432&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/192769/original/file-20171101-13425-1tmjpcn.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=432&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/192769/original/file-20171101-13425-1tmjpcn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=543&fit=crop&dpr=1 754w, https://images.theconversation.com/files/192769/original/file-20171101-13425-1tmjpcn.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=543&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/192769/original/file-20171101-13425-1tmjpcn.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=543&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Bull sharks can roam in rivers as well as oceans.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File%3ABullshark.JPG">Albert Kok/Wikimedia Commons</a></span>
</figcaption>
</figure>
<h2>Opportunistic tigers</h2>
<p>Tiger sharks <a href="http://onlinelibrary.wiley.com/doi/10.1111/jfb.12887/abstract">mainly stay in coastal waters</a>, although they also venture into the open ocean. Their movements are unpredictable, they eat a wide range of prey, are naturally curious and opportunistic, and can be aggressive to humans. </p>
<p>Tiger sharks are clever too – they are thought to use <a href="https://www.researchgate.net/publication/225625331_A_multiple_instrument_approach_to_quantifying_the_movement_patterns_and_habitat_use_of_tiger_Galeocerdo_cuvier_and_Galapagos_sharks_Carcharhinus_galapagensis_at_French_Frigate_Shoals_Hawaii">“cognitive maps” to navigate between distant foraging areas</a>, and have <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0116916">hunting ranges that span hundreds of thousands of square kilometres</a> so as to maintain the element of surprise. As a result, tiger sharks’ distribution in Australian waters covers all but the country’s southern coast.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/192771/original/file-20171101-13408-cerr2g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/192771/original/file-20171101-13408-cerr2g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/192771/original/file-20171101-13408-cerr2g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=320&fit=crop&dpr=1 600w, https://images.theconversation.com/files/192771/original/file-20171101-13408-cerr2g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=320&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/192771/original/file-20171101-13408-cerr2g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=320&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/192771/original/file-20171101-13408-cerr2g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=403&fit=crop&dpr=1 754w, https://images.theconversation.com/files/192771/original/file-20171101-13408-cerr2g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=403&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/192771/original/file-20171101-13408-cerr2g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=403&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tiger sharks like to keep their prey guessing.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File%3ATigershark3.jpg">Albert Kok/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/finally-a-proven-way-to-keep-great-white-sharks-at-arms-length-61986">Finally, a proven way to keep great white sharks at arm's length</a>
</strong>
</em>
</p>
<hr>
<p>Taken together, it’s clear that Australia’s waters are home to three predators that can pose a real danger, even if only an accidental one, to humans.</p>
<p>But remember that shark attacks are incredibly rare events, and fatal ones even rarer still. There are also lots of <a href="https://taronga.org.au/animals-conservation/conservation-science/australian-shark-attack-file/prevention-shark-attacks">tips we can use</a> to minimise the risk of having a negative encounter with a shark. </p>
<p>Don’t swim in murky, turbid or dimly lit water, as sharks may not be able to see you properly (and you may not be able to see them). Avoid swimming in canals, or far from the shore, or along dropoffs. Swim in designated areas and with others, and avoid swimming where baitfish (or bait) may be present. And of course, always trust your instincts.</p><img src="https://counter.theconversation.com/content/85986/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Blake Chapman is affiliated with The University of Queensland as an Adjunct Research Fellow. </span></em></p>Fatal shark bites are very rare. But the stats do suggest that the likelihood of an attack proving fatal is higher in Australia - probably because our waters are home to the “big three” dangerous species.Blake Chapman, Adjunct Research Fellow, Science Communicator, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/773992017-06-06T21:34:09Z2017-06-06T21:34:09ZCurious Kids: Do sharks sneeze?<figure><img src="https://images.theconversation.com/files/168515/original/file-20170509-20740-88e7iq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A shark's nose is chemosensory only, and it doesn’t join up to the back of the throat like ours does.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/leszekleszczynski/15447205451/in/photolist-px1Y1t-7AEZ2k-bMdCJ-Fsd6W-5HxWS-ek4Kv-21JtHU-cTV86-hPj18-WcigB-nbyoWA-GXtnA-9DGyME-6J8zm6-2eQkE-H28kr-9iiHZw-2VJce-rzEF8E-ek4KQ-4WjDVM-SXTa9-Wcig2-okzhU-aCvQE-6AKPRc-6SDamw-21u3i-21tZy-2gotK6-4K2qPB-ewqf-eMc7DJ-4K2qQp-JVfnt-7S3cGe-73boiZ-peS1wL-8auYco-a2QZa-hL3ps-6APYYG-73EmD9-gE6gjW-mGkjW-4Utjxk-2Bjt37-4mJ1cb-RY8Esq-orHiFR">Flickr/Leszek Leszczynski</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a new series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!</em> </p>
<hr>
<blockquote>
<p><strong>Do sharks sneeze? – Desmond, aged 4, Perth.</strong></p>
</blockquote>
<p>When an animal sneezes, it’s their way of getting rid of annoying bits and pieces that have floated inside their nose and mouth.</p>
<p>While many animals, including <a href="https://www.youtube.com/watch?v=fyEajHy8Fzg">humans</a>, <a href="https://youtu.be/gtIz1u8g1F0">elephants</a>, <a href="https://youtu.be/93hq0YU3Gqk">pandas</a> and even <a href="https://www.youtube.com/watch?v=oGIlaSz9eHE">seals</a>, can sneeze, sharks unfortunately cannot. To be able to sneeze, an animal needs to move air (or water) from the lungs through its nose to the outside. </p>
<p>Sharks have two nostrils (called nares) below their snout that are used for smelling, but they don’t join up to the back of the throat like our nose does, so they can’t sneeze like we do. If something floats into their nares, they might try to shake it out.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/171560/original/file-20170531-23681-1bkxgaq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/171560/original/file-20170531-23681-1bkxgaq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/171560/original/file-20170531-23681-1bkxgaq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=395&fit=crop&dpr=1 600w, https://images.theconversation.com/files/171560/original/file-20170531-23681-1bkxgaq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=395&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/171560/original/file-20170531-23681-1bkxgaq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=395&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/171560/original/file-20170531-23681-1bkxgaq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=496&fit=crop&dpr=1 754w, https://images.theconversation.com/files/171560/original/file-20170531-23681-1bkxgaq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=496&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/171560/original/file-20170531-23681-1bkxgaq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=496&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Shark nostrils are called nares, but they do their breathing through their gills at the back of the mouth.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/lwpkommunikacio/14663970488/in/photolist-okNFxo-9NJybd-9NH9LR-8XQBnd-7kRvAK-ck8vcw-tHyeg6-9Nvxqd-CXXxV-9NAqQe-dugcMs-9NFVNX-9Nv8dj-9NEYMC-9NC9uz-4nmqPS-okP83k-9NvF6h-batHzF-6UGb1b-oC2r7v-p3RRp-p3QxL-adqDCb-dthtvX-aCPgav-9NDgMs-6Yz65f-5uJfYR-4nmqP5-4nhn2p-batHBa-batHyZ-4nhmUn-7co5Fo-rLXuC3-4nmqMm-6ADiza-amvWHZ-4RZRhc-4jmHMm-64FHLp-2kbyNw-5uNEcd-7bZkvH-5uJfcn-4KVtqJ-7co7Qb-559aXg-7cjgNR">Flickr/Lwp Kommunikáció</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Sharks breathe through the gills at the back of the mouth. Most of their “smelling” is done using a process called chemoreception, which allows sharks to sense tiny pieces of stuff, called molecules, hiding in the water as they pass through their nares.</p>
<p>Sharks can find and recognise these molecules – like parts of blood – that have been released from wounded animals or other prey, because their sense of smell is much better than ours. </p>
<p>Nares are loaded with powerful sensors. Once a shark has locked onto a smell, it can then work out where it came from by swimming towards it and moving its head slightly from side to side. It’s a bit like us following the smell of a freshly baked cake. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/171559/original/file-20170531-23660-1sywmg3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/171559/original/file-20170531-23660-1sywmg3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/171559/original/file-20170531-23660-1sywmg3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/171559/original/file-20170531-23660-1sywmg3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/171559/original/file-20170531-23660-1sywmg3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/171559/original/file-20170531-23660-1sywmg3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/171559/original/file-20170531-23660-1sywmg3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/171559/original/file-20170531-23660-1sywmg3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">It’s an exaggeration to say a shark can smell a single drop of blood in the ocean. But they might be able to smell tiny drops of blood in the water from up to five kilometres away.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/elevy/14730820387/in/photolist-orHiFR-86TtTf-7s62o-cfcR4-oJZUAK-FXJoL-7eLhsZ-49GjB8-cfWquS-551zjf-aJA7uv-6SQ6f3-mAQBh-78N7QT-b2dvkB-uAAvu-nNEH67-49GjJK-R6Pe-Vpfrz-kJsJbm-7bXmoE-49Lp8G-4AFffU-4KC2sV-CnoYi-5kStmp-9KKwc-jsEYG-eRDuu-8z3sa5-4VE1N3-bASq9s-bJatC-csBe15-5vUKUf-zzc7Y-4KnYic-j7dMVY-orHaNh-oGazeC-oHVAYR-map2Gv-orHgL8-QmN9g3-orGUyS-8wSLbJ-UPqA7d-5tUai4-orGNVX">Flickr/Elias Levy</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Legend has it that sharks can smell a single drop of blood in the ocean, but that’s an exaggeration. What they <em>can</em> do is detect blood at one part per million, which is similar to detecting tiny drops of blood in the water from up to five kilometres away!</p>
<p>While some have claimed to capture sightings of <a href="https://www.google.com.au/search?q=youtube+shark+nose&oq=youtube+shark+nose&aqs=chrome..69i57j0j69i60l3j0.1979j0j4&sourceid=chrome&ie=UTF-8#q=youtube+shark+sneeze">sharks sneezing on video</a>, it just isn’t physically possible.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/ifM3H-oiR6k?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">You might think this shark is sneezing, but trust me – it’s not.</span></figcaption>
</figure>
<p>The movement people confuse with sneezing is likely the animal’s attempt at getting rid of unwanted objects from their mouth or stomach area. </p>
<p>Sharks can actually make their stomach stick out of their mouth for brief moments to get rid of things they have eaten that they don’t like, such as tyres, licence plates, fish bones and fish hooks. This is called <a href="http://infinitespider.com/stomach-eversion-in-five-animals/">gastric eversion</a> and it’s a very cool trick.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/eoJdOOYfe4s?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Gastric eversion is where a shark or other animal empties its stomach by making it stick out of their mouth.</span></figcaption>
</figure>
<p>Alternatively, a shark stretching its jaws, which they sometimes do after a meal, might be mistaken for a sneeze.</p>
<p>While sharks can’t sneeze like we do, they can smell and they have other great ways of getting rid of unwanted things from inside them.</p>
<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. They can:</em></p>
<p><em>* Email your question to curiouskids@theconversation.edu.au
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<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><em>Please tell us your name, age, and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/77399/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jane Williamson does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Sharks can’t sneeze like we do, but they can do other cool tricks – like making their stomach stick out of their mouth to get rid of unwanted stuff.Jane Williamson, Associate Professor in Marine Ecology, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/716332017-02-12T19:09:34Z2017-02-12T19:09:34ZHow drones can help fight the war on shark attacks<p>Following an <a href="https://taronga.org.au/conservation/conservation-science-research/australian-shark-attack-file">unprecedented series of shark attacks</a> off Australian beaches, the need to find practical solutions is intensifying. </p>
<p>Aerial drones could be an important tool for reducing risk of shark attacks on our beaches within the coming years. Here’s how it would work. Drones would fly autonomously over beaches continuously scanning for sharks with image recognition software. </p>
<p>If a shark is detected, real-time video will be instantly sent to beach authorities, such as lifeguards. If it is a dangerous shark, appropriate action can be taken to ensure public safety, such as sounding alarms and clearing people from the water.</p>
<p>Like other shark bite mitigation measures, this cannot completely eliminate the possibility of a shark attack. However, it could help to reduce the risk to an acceptable level for the majority of beach users.</p>
<p>Importantly, the drone-based approach to shark bite mitigation does not harm sharks or other marine wildlife, such as whales, dolphins, rays and sea turtles, unlike more controversial shark control measures such as mesh nets or baited drum lines.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/iCcMT4r5Mik?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Surfer has a close encounter with a great white shark as seen by a drone.</span></figcaption>
</figure>
<h2>Testing drones</h2>
<p>As part of the NSW government’s A$16 million <a href="http://www.dpi.nsw.gov.au/fishing/sharks/shark-management">Shark Management Strategy</a>, researchers from the NSW Department of Primary Industries (NSW DPI) and Southern Cross University (SCU) have demonstrated that drones can reliably detect sharks off Australian beaches. </p>
<p>NSW DPI researchers have also compared the costs and benefits of marine wildlife sightings between drones and helicopters, as well as established environmental conditions suitable for drones to provide effective shark detection capabilities.</p>
<p>This summer, a team of SCU and DPI researchers completed an intensive <a href="https://www.youtube.com/watch?v=NnWhF3D6OxI&feature=youtu.be">drone trial</a> on five important beaches in NSW to verify that drones will work in the long term. As part of the trial, drones performed six 20-minute patrols each morning on each beach for every day of the school holidays. </p>
<p>Researchers monitoring drone footage spotted great white, bull, whaler, mako and hammerhead sharks off NSW beaches. They also saw many dolphins, sea turtles and less dangerous shark species, such as shovel-nosed sharks.</p>
<p>These trials included experiments comparing “people versus machines” by evaluating the utility of automated flight paths and shark recognition software. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/tlVNr81KZt8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Drone captures a great white shark cruising the shallows of Northern NSW.</span></figcaption>
</figure>
<h2>Automating the drone-based approach</h2>
<p>The overall objective of this research is to develop a fully automated drone-based shark surveillance system in the near future.</p>
<p>We envisage that a team of aerial drones could run continuous shark detection missions during the hours when most people are on our beaches.</p>
<p>When required, each drone will automatically take off, patrol for sharks, land itself and charge up again, ready for the next mission. If a drone detects a shark, to can alert beach authorities.</p>
<p>Their response will vary depending on the species of shark detected and its location. This will be immediately apparent from the live video feed and location data they receive. As well as tracking sharks, the drones will also be fitted with sirens and lights to contribute to any emergency actions.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/aIEN3Af17kg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Great white shark off a beach in Northern NSW.</span></figcaption>
</figure>
<h2>Problems to solve</h2>
<p>There are still at least five major challenges to overcome before establishing a fully functional automated drone-based shark surveillance system. But these could be gradually overcome within the next few years.</p>
<p><strong>Civil aviation regulations</strong></p>
<p><a href="https://theconversation.com/got-a-drone-for-christmas-know-the-law-before-taking-to-the-skies-70341">Aviation regulations</a> restrict the use of fully automated drones in most airspace. We could overcome this problem by modifying the law or establishing restricted zones over beaches where drones can fly.</p>
<p><strong>Public safety concerns</strong></p>
<p>We need to minimise the risk of injury as a result of drone failure, by making sure their flight components are failsafe and having flight paths clear of beachgoers. We also need airspace safety systems to ensure that drones are grounded when emergency and other aircraft are in the vicinity.</p>
<p><strong>Public privacy concerns</strong></p>
<p>A drone-based shark surveillance system would require public acceptance. For this, beachgoers need to be aware of the sorts of data being collected by the drones, and to rest assured that this does not breach privacy legislation.</p>
<p><strong>Reliable hardware</strong></p>
<p>Although aerial drones can already automatically take off, fly routes, land and charge themselves, it is not clear how reliably this technology will stand up to the Australian beach environment. To be effective, we will need drones that can reliably function under heavy workloads in coastal conditions. Similarly, data transfer platforms also need to be fast and reliable.</p>
<p><strong>Purpose-designed software</strong></p>
<p>Image analysis software needs to be further developed to automatically detect sharks with a high level of accuracy. Customised software will also need to be developed to coordinate the missions of a team of drones and to ensure seamless video streaming to the portable wireless devices of beach authorities and users.</p>
<p>In terms of the hardware and software challenges, there are a number of research groups racing towards solutions with the goal of commercialising their products. Once an automated drone-based technology for shark bite mitigation is in place, it should be possible to solve issues regarding legislation, safety and privacy.</p>
<p>Given the current rate of technological development and the falling costs of commercially available drones, fully automated drones could be reducing the risk of shark attacks on Australian beaches within five years. However, for many nervous beachgoers, this may not be soon enough.</p><img src="https://counter.theconversation.com/content/71633/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brendan Kelaher receives funding from the NSW Department Primary Industries for two PhD students working on shark projects. </span></em></p><p class="fine-print"><em><span>Andrew Colefax receives project funding for his PhD from the NSW Department of Primary Industries (NSW DPI). He also receives additional work from the NSW DPI.</span></em></p><p class="fine-print"><em><span>Paul Butcher works for NSW Department of Primary Industries. He receives funding from the NSW and Commonwealth Governments. He is an Adjunct Associate Professor at Southern Cross University.</span></em></p><p class="fine-print"><em><span>Vic Peddemors receives funding from the NSW Government, the Australian Research Council and the Fisheries Research and Development Corporation (FRDC) on behalf of the Australian Government. </span></em></p><p class="fine-print"><em><span>Bob Creese does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>LIfeguards could potentially have a new ally in the fight to reduce shark incidents: drones that can spot when a shark swims nearby, and automatically alert authorities.Brendan Kelaher, Associate Professor of Marine Science and Management, Southern Cross UniversityAndrew Colefax, Phd candidate, Southern Cross UniversityBob Creese, Adjunct professor, Southern Cross UniversityPaul Butcher, Adjunct Professor, Southern Cross UniversityVic Peddemors, Shark Biology & Assessment, Sydney Institute of Marine ScienceLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/694002016-12-08T19:05:24Z2016-12-08T19:05:24ZNot just nets: how to stop shark attacks without killing sharks<figure><img src="https://images.theconversation.com/files/148994/original/image-20161207-25742-q76c3k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Shelly Beach near Ballina, one of the new shark net locations, was the scene of a fatal shark attack in February 2015.</span> <span class="attribution"><a class="source" href="http://one.aap.com.au/#/search/Shark%20attack%20ballina?q=%7B%22pageSize%22:25,%22pageNumber%22:1%7D">Dave Hunt/AAP</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>The recent <a href="http://www.abc.net.au/news/2016-10-12/ballina-beaches-closed-after-shark-attack-off-nsw-north-coast/7925624">spate of shark attacks</a> in New South Wales has led to the announcement by NSW Premier Mike Baird and Primary Industries Minister Niall Blair of an expansion of the <a href="http://www.dpi.nsw.gov.au/fishing/sharks/management/shark-meshing-bather-protection-program">Shark Meshing Bather Protection Program</a>. New shark nets are being installed at five locations in the Ballina and Evans Head area of the state’s north coast. </p>
<p>However, shark nets are controversial because they are designed to kill potentially dangerous sharks. In the process, nets may also <a href="http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0007/623248/shark-meshing-bather-protection-program-2014-15-annual-performance-report.pdf">injure or kill non-target animals</a>, including endangered and protected species. </p>
<p>Whether or not shark nets actually reduce the risk of an attack is also a <a href="https://theconversation.com/it-will-take-years-to-know-whether-new-south-wales-shark-nets-are-working-69635">tricky question</a>, although there has <a href="http://www.dpi.nsw.gov.au/fishing/sharks/management/shark-meshing-bather-protection-program">only been one fatal attack</a> at a netted beach since the NSW meshing program began in 1937.</p>
<p>While some people welcome more nets, there is <a href="http://www.abc.net.au/news/2016-10-23/hundreds-rally-against-shark-net-plans-in-ballina/7958068">increasing support</a> for the use of non-lethal shark attack mitigation measures. This is largely driven by concerns about the potential ecological impacts of shark nets. However, there are also substantial economic and logistical constraints on deploying nets at all locations where people might enter the water.</p>
<h2>Beyond shark nets</h2>
<p>So what other strategies can we use? As well as enhancing public awareness of attack risk, a range of shark attack mitigation measures have become available. In addition to shark nets, shark-proof barriers and early warning systems can be used as large-scale initiatives to reduce shark attack risks at popular beaches. </p>
<p>Concern about shark attacks has also led to a proliferation of personal shark deterrent technologies – so much so that there are now too many to list and describe in detail.</p>
<p>Broadly, currently available devices include those that produce strong electrical or magnetic fields, those that produce a repulsive light, sound or odour, and those that reduce the visibility of the wearer to sharks.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/148991/original/image-20161207-25753-pfhe87.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/148991/original/image-20161207-25753-pfhe87.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=571&fit=crop&dpr=1 600w, https://images.theconversation.com/files/148991/original/image-20161207-25753-pfhe87.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=571&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/148991/original/image-20161207-25753-pfhe87.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=571&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/148991/original/image-20161207-25753-pfhe87.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=717&fit=crop&dpr=1 754w, https://images.theconversation.com/files/148991/original/image-20161207-25753-pfhe87.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=717&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/148991/original/image-20161207-25753-pfhe87.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=717&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Shark net trial locations, NSW north coast.</span>
<span class="attribution"><a class="source" href="http://www.dpi.nsw.gov.au/fishing/sharks/management/shark-net-trial">NSW Department of Primary Industries.</a></span>
</figcaption>
</figure>
<h2>Can new devices prevent attacks?</h2>
<p>Because of the upsurge in technologies being developed to reduce shark attacks, shark researchers are often asked which are the most effective deterrent devices and which do not work.</p>
<p>However, many of these technologies are still in development. Fewer still have undergone <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0062730">independent testing</a> of their effectiveness in deterring sharks under <a href="http://journals.plos.org/plosone/article?id=info:doi/10.1371/journal.pone.0157717">different conditions</a>. This means that the general public have limited information when deciding if a particular shark deterrent might be suitable and whether it is worth purchasing, especially given that most commercially available devices cost several hundred dollars.</p>
<p>Our current research focuses on the new generation of magnetic and electrical deterrents, especially those designed to be used or worn by surfers and swimmers. We will test these devices in the field with white sharks to assess their efficacy. In the case of the electrical devices, we will map the electrical fields they emit to assess the strength and shape of these fields. </p>
<p>Importantly, by combining these approaches, we can correlate electric field strength with actual deterrent efficiency. This will help to streamline the development and testing of such devices by weeding out prototypes that do not work because their electrical fields are too weak to repel a motivated shark.</p>
<h2>Fundamental shark research is essential</h2>
<p>Our research will also focus on the physiological response of the shark’s electroreceptive system to the devices’ electrical and magnetic fields. This information will provide an improved biological understanding of the effect of these different stimuli on the sharks’ senses.</p>
<p>History shows that developing shark deterrents based on what we know about shark sensory biology is <a href="http://onlinelibrary.wiley.com/doi/10.1111/1749-4877.12095/abstract">far more efficient</a> than a trial-and-error approach. This research will also assist in adapting some of the personal deterrent technologies or concepts for use at a larger scale, such as the electric shark barrier being trialled in <a href="http://www.shark.co.za/Pages/SharkRepellentTechnology">South Africa</a>.</p>
<p>Any shark attack can be traumatising to the people directly or indirectly involved, and it is critical to reduce risks as much as possible. However, it is also important that manufacturers, scientists and governmental agencies do not overstate their ability to reduce risks of a shark attack.</p>
<p>The general public should be aware that there is no magic bullet when it comes to preventing attacks. No deterrent will prevent every shark attack in every situation. </p>
<p>The only way to remove all risk of an attack is to swim within a well-maintained enclosure that excludes sharks by means of an impervious barrier, or to stay out of the water altogether. </p>
<p>For those determined to venture further into the ocean, we encourage responsible <a href="http://www.dpi.nsw.gov.au/fishing/sharks/sharksmart">SharkSmart behaviour</a>. This includes staying close to shore, swimming in groups and avoiding large schools of bait fish.</p>
<p><em>This article was updated December 9 to clarify strategies used to mitigate shark attacks.</em></p><img src="https://counter.theconversation.com/content/69400/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathan Hart has received research funding from the Australian Research Council Linkage Program, The State Government of Western Australia Applied Research Program, The NSW DPI Small Grant Program and the Sea World Research and Rescue Foundation to study shark sensory systems and shark deterrents. He has provided design criteria (under contract) to companies that market shark deterrent wetsuits (Shark Mitigation Systems) and advice (based on our independent testing) to companies that produce electronic shark deterrent devices (Shark Shield).</span></em></p><p class="fine-print"><em><span>Charlie Huveneers receives funding from NSW DPI Small Grant Program. </span></em></p>Shark nets are controversial, which is why the New South Wales government is investigating a host of other ways to keep humans and sharks apart – some more tried and tested than others.Nathan Hart, Associate Professor of Biological Sciences, Macquarie UniversityCharlie Huveneers, Senior lecturer, Flinders UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/640682016-08-17T14:51:12Z2016-08-17T14:51:12ZStop freaking out about sharks in British waters – let’s welcome them<figure><img src="https://images.theconversation.com/files/134481/original/image-20160817-3608-hopj97.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Mako sharks look fearsome, but they eat fish not people.</span> <span class="attribution"><span class="source">Alessandro De Maddalena / shutterstock</span></span></figcaption></figure><p>Summer seems to have finally arrived, and many people are enjoying the temporary warmth of the British coastlines. Unfortunately, this has been accompanied by a plethora of <a href="https://theconversation.com/how-jaws-kicked-off-our-40-year-love-affair-with-sharks-42858">Jaws-inspired</a> shark sightings and lurid newspaper articles. </p>
<p>I’m here to tell you to ignore those headlines. Sharks in the British Isles are something to be cherished, not feared.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/134444/original/image-20160817-3573-w99b8j.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/134444/original/image-20160817-3573-w99b8j.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/134444/original/image-20160817-3573-w99b8j.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=676&fit=crop&dpr=1 600w, https://images.theconversation.com/files/134444/original/image-20160817-3573-w99b8j.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=676&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/134444/original/image-20160817-3573-w99b8j.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=676&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/134444/original/image-20160817-3573-w99b8j.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=850&fit=crop&dpr=1 754w, https://images.theconversation.com/files/134444/original/image-20160817-3573-w99b8j.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=850&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/134444/original/image-20160817-3573-w99b8j.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=850&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Nothing to see here.</span>
<span class="attribution"><a class="source" href="https://www.thesun.co.uk/news/uknews/1619939/new-evidence-a-killer-shark-is-stalking-the-british-coast-after-terrifying-beast-is-eaten-alive/">The Sun</a></span>
</figcaption>
</figure>
<p>Every year newspapers <a href="https://theconversation.com/its-silly-season-but-there-is-a-real-shark-threat-to-fear-16975">sensationalise shark sightings</a>, taking every opportunity to sell more papers and have fleeting fame with <a href="https://www.thesun.co.uk/news/uknews/1619939/new-evidence-a-killer-shark-is-stalking-the-british-coast-after-terrifying-beast-is-eaten-alive/">viral articles</a>. While our fascination with sharks is undeniable, whether it is from admiration or fearfulness, many of these articles are misrepresenting sharks and creating unnecessary panic among beachgoers.</p>
<p>UK waters are home to many more beautiful and varied sharks than you might initially think. Ranging from the smaller species such as lesser-spotted catsharks and the glow in the dark <a href="https://twitter.com/sharkdevocean/status/697436696359657472">velvet belly lantern sharks</a>, all the way through to the huge basking sharks and even sometimes <a href="https://theconversation.com/a-400-year-old-shark-is-the-latest-animal-discovery-to-reveal-the-secrets-of-long-life-63784">greenland sharks</a>, about 40 species can be found around the British Isles.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"406449293675855872"}"></div></p>
<p>This includes year-round residents such as smoothhounds, or <a href="https://sharkdevocean.wordpress.com/2014/07/04/sharking-in-the-mediterranean-part-2/">black mouth catsharks</a>, but also seasonal visitors. During the summer months, warming waters bring in fish such as mackerel and sprat as they migrate in from southerly or offshore waters to feed. Migratory blue, mako and thresher sharks often follow this temporary flux of smaller fish, all visiting local waters to feed within these summer festivals of fish.</p>
<h2>The ‘Jaws of Cornwall’ probably doesn’t exist</h2>
<p>Every year without fail, claims start appearing that a huge great white shark has been <a href="http://www.dailymail.co.uk/travel/travel_news/article-3576853/Holidaymakers-fear-great-white-shark-lurking-UK-coast-mutilated-porpoise-washes-popular-beach.html">seen somewhere near the UK</a>. This poster species is occasionally spotted in Europe, but to date there have been no confirmed sightings or catches in the UK. Considering the huge amount of fishing that occurs off British shores, if the island did have regular visits from white shark, I’m sure we would have seen one by now.</p>
<p>Large shark sightings can usually be attributed to a few species. Most tend to be the bus-sized basking shark. This leviathan of a shark is completely harmless though. Being a filter feeder, it can often be seen swimming around Cornwall or the Hebrides with its mouth wide open, hoovering up sudden blooms of tiny animals such as plankton.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/134450/original/image-20160817-3571-1m5b3pt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/134450/original/image-20160817-3571-1m5b3pt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/134450/original/image-20160817-3571-1m5b3pt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=322&fit=crop&dpr=1 600w, https://images.theconversation.com/files/134450/original/image-20160817-3571-1m5b3pt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=322&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/134450/original/image-20160817-3571-1m5b3pt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=322&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/134450/original/image-20160817-3571-1m5b3pt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=405&fit=crop&dpr=1 754w, https://images.theconversation.com/files/134450/original/image-20160817-3571-1m5b3pt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=405&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/134450/original/image-20160817-3571-1m5b3pt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=405&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Lookout, plankton! Basking shark spotted at Porthcurno Beach, Cornwall.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/candiche/299049845/">candiche</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Close relatives porbeagle and mako sharks are also often misidentified as white sharks. While similar in shape to the untrained eye, these sharks have more of a taste for fast swimming <a href="http://icesjms.oxfordjournals.org/content/59/6/1263.short">fish</a> and <a href="http://link.springer.com/article/10.1007/s10641-006-9067-7">squid</a>.</p>
<p>Although <a href="http://www.dailymail.co.uk/travel/travel_news/article-3576853/Holidaymakers-fear-great-white-shark-lurking-UK-coast-mutilated-porpoise-washes-popular-beach.html">mauled marine life</a> does sometimes wash ashore, sparking tabloid fears of monster sharks, these injuries are often the work of boat propellers, <a href="https://theconversation.com/grey-seals-in-the-dock-over-porpoise-murder-mystery-34690">seals</a> and scavenging birds or fish. </p>
<h2>Hidden depths</h2>
<p>A huge proportion of Britain’s shark diversity will unfortunately go almost entirely unseen. These are the wonderfully alien deep-sea sharks and the British Isles have an <a href="https://theconversation.com/meet-the-ghost-sharks-and-deep-sea-demons-that-will-haunt-your-dreams-49325">astonishing variety</a> of them. There are about 26 species of deep-sea shark that live in waters from 500 metres down to 2,500 metres and can be found in the deep-water off the west coast of Scotland and Ireland.</p>
<p>Despite the incredible number of different shark species in British waters, there has never once been a fatal “attack” on humans. Although, in 1937, a basking shark capsized a boat in Kintyre, Scotland, causing all three crew members to drown. But the rare bites that have <a href="https://owlcation.com/stem/Shark-Attacks-in-British-Waters">been documented</a> are often sustained by recreational fishermen while trying to tackle sharks onto their boats.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/134491/original/image-20160817-3569-1uab3pw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/134491/original/image-20160817-3569-1uab3pw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/134491/original/image-20160817-3569-1uab3pw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=339&fit=crop&dpr=1 600w, https://images.theconversation.com/files/134491/original/image-20160817-3569-1uab3pw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=339&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/134491/original/image-20160817-3569-1uab3pw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=339&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/134491/original/image-20160817-3569-1uab3pw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=426&fit=crop&dpr=1 754w, https://images.theconversation.com/files/134491/original/image-20160817-3569-1uab3pw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=426&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/134491/original/image-20160817-3569-1uab3pw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=426&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Huge but harmless – another basking shark spotted off England’s south coast.</span>
<span class="attribution"><a class="source" href="http://www.exeter.ac.uk/esi/people/phd_students/doherty/">Phil Doherty</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Humans pose a much greater threat to sharks than they do to us. A recent study in the North Sea found that high levels of fishing, climate changes and habitat destruction have likely <a href="http://onlinelibrary.wiley.com/doi/10.1111/gcb.13316/abstract">caused significant changes in shark numbers</a> over the past century. Additionally, severe declines in other larger species such as the <a href="http://www.iucnredlist.org/details/11200/0">porbeagle</a> and mako sharks have also been blamed on heavy unregulated fishing.</p>
<p>Although many fisheries are required to adhere to strict fishing quotas, there are currently <a href="http://www.sharktrust.org/en/no_limits">no annual limits for certain species of European sharks</a>. About a hundred millions sharks are <a href="http://www.sciencedirect.com/science/article/pii/S0308597X13000055">killed globally every year,</a> often targeted for their fins which are then sold to Asian markets for shark fin soup. In recent years, as other fish stocks have declined, <a href="http://www.fao.org/3/a-i4795e.pdf">shark meat is increasingly making its way on to the market</a> though.</p>
<p>Unless science-based regulations are implemented in the near future, UK shark sightings, while already rare, may disappear altogether. So if you do see a shark in British waters this summer, don’t panic – you just got lucky. </p>
<figure>
<iframe src="https://player.vimeo.com/video/124152869" width="500" height="281" frameborder="0" webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen=""></iframe>
<figcaption><span class="caption">These people in West Cork, Ireland, just got lucky.</span></figcaption>
</figure><img src="https://counter.theconversation.com/content/64068/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christopher Bird does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>If you do see a shark this summer, don’t panic – you just got lucky.Christopher Bird, Ph.D candidate: Shark Ecology, University of SouthamptonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/619862016-07-04T20:07:14Z2016-07-04T20:07:14ZFinally, a proven way to keep great white sharks at arm’s length<figure><img src="https://images.theconversation.com/files/129144/original/image-20160704-19121-tmw757.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An electric field could help avoid getting any closer than this.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File%3ACarcharodon_carcharias.jpg">Sharkdiver.com/Wikimedia Commons</a></span></figcaption></figure><p>A wearable electric shark deterrent can effectively repel great white sharks, according to our independent tests of the device. </p>
<p>The manufacturers of the A$749 <a href="https://sharkshield.com/shop/freedom7/">Shark Shield Freedom 7TM</a> say it works by emitting an electric field around the wearer. This causes uncomfortable muscle spasms in sharks that swim too close and discourages them from coming into contact.</p>
<p>Our research, published in the journal <a href="http://journals.plos.org/plosone/article?id=info%3Adoi%2F10.1371%2Fjournal.pone.0157717">PLoS ONE</a>, shows that the device does indeed make sharks keep their distance. Upon first encounter with a Shark Shield, all approaching great white sharks were effectively deterred, staying an average of 1.3m away from a baited canister with the device attached.</p>
<p>After multiple approaches, individual great white sharks showed signs of habituation to the Shark Shield, coming an average of 12cm closer on each successive approach. Despite this increase in tolerance, 89% of white sharks continued to be deterred from biting or interacting with the bait.</p>
<h2>Don’t take the bait</h2>
<p>We carried out our testing in Mossel Bay, South Africa, in 2014. We used custom-built cameras equipped with bait and either an inactive (control) or active Shark Shield. Using a video analysis technique traditionally used to measure the size of fish, we were able to determine exactly how closely the sharks approached the device. </p>
<p>We analysed a total of 322 encounters involving 41 individual white sharks, ranging from 2m to 4m long.</p>
<p>Only one great white shark came into contact with the bait in the presence of an active Shark Shield, and only after multiple approaches. The interaction in question simply involved a bump of the bait canister rather than a full bite. In contrast, bites were common during control trials.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/129141/original/image-20160704-19103-870eas.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/129141/original/image-20160704-19103-870eas.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/129141/original/image-20160704-19103-870eas.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=224&fit=crop&dpr=1 600w, https://images.theconversation.com/files/129141/original/image-20160704-19103-870eas.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=224&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/129141/original/image-20160704-19103-870eas.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=224&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/129141/original/image-20160704-19103-870eas.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=282&fit=crop&dpr=1 754w, https://images.theconversation.com/files/129141/original/image-20160704-19103-870eas.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=282&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/129141/original/image-20160704-19103-870eas.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=282&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Test footage with the Shark Shield switched on (left) and turned off (right).</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Although the effectiveness of the Shark Shield probably varies between shark species, it is encouraging to note its effect on great white sharks, the species <a href="http://www.flmnh.ufl.edu/fish/isaf/contributing-factors/species-implicated-attacks">implicated in the majority of fatal incidents worldwide</a>. This suggests it could be an important safety consideration for a range of ocean users such as surfers, divers, spear fishers and open-water swimmers.</p>
<p>We also found no evidence that the Shark Shield attracted sharks from further away, which is a common myth among surfers.</p>
<h2>A useful tool</h2>
<p>Besides showing that the Shark Shield can ward off sharks, our method provides an accurate way to test the effectiveness of any type of shark deterrent that is currently available or likely to enter the market. </p>
<p>But, most importantly for now, we have finally given the public some evidence that there is an effective way to reduce the risk of a negative encounter with a shark. </p>
<p>Instead of the <a href="https://theconversation.com/shark-bite-statistics-can-lie-and-the-result-is-bad-policy-21789">redundant debate</a> about <a href="https://theconversation.com/au/topics/wa-shark-cull">culling sharks</a> as a response to shark-bite incidents, ocean-goers can now proactively take extra precautions, by using proven technology to reduce their already very low risk of injury.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/129142/original/image-20160704-19118-np9fw8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/129142/original/image-20160704-19118-np9fw8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/129142/original/image-20160704-19118-np9fw8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=355&fit=crop&dpr=1 600w, https://images.theconversation.com/files/129142/original/image-20160704-19118-np9fw8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=355&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/129142/original/image-20160704-19118-np9fw8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=355&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/129142/original/image-20160704-19118-np9fw8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=446&fit=crop&dpr=1 754w, https://images.theconversation.com/files/129142/original/image-20160704-19118-np9fw8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=446&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/129142/original/image-20160704-19118-np9fw8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=446&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Ryan Kempster gets up close and personal with a great white.</span>
<span class="attribution"><span class="source">Channing Egeberg</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>There are many shark deterrent devices on the market, particularly those that use electric or magnetic fields. But without robust, independent scientific evaluation we can’t be sure which of these products actually work. In fact, not only may some devices not be as effective as others, but it is also possible that some of them could actually attract sharks rather than repel them.</p>
<p>Robust scientific evaluation of these types of devices will help the public make informed decisions about how they can reduce their risk of encountering a shark.</p>
<p>It’s important to note that the likelihood of being involved in a negative encounter with a shark is exceptionally low. As a result, some will argue that the use of expensive technology to mitigate that risk even further is unnecessary. Furthermore, no device is likely to guarantee 100% protection from any species of shark.</p>
<p>But at present, under the conditions in which we tested it, this is one device that does seem to offer a genuine benefit. So if you feel that you need extra protection from sharks when entering the water, this device will offer you exactly that.</p>
<p><em>This article was written with the help of Channing Egeberg, a University of Western Australia marine euroecology MSc graduate and cofounder of <a href="http://www.supportoursharks.com/">Support our Sharks</a>.</em></p><img src="https://counter.theconversation.com/content/61986/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ryan Kempster received funding from WA State Government Shark Hazard Mitigation Applied Research Program, which provided over $220,000 for this research as part of a larger package to investigate the effectiveness of existing shark deterrents. He is also affiliated with the non-profit shark conservation group Support Our Sharks. </span></em></p><p class="fine-print"><em><span>Shaun Collin received funding from the WA State Government Shark Hazard Mitigation Applied Research Program, which provided $220,000 for this research. </span></em></p>Independent tests show that a wearable electric deterrent called a Shark Shield does indeed seem to live up to its name.Ryan Kempster, Shark biologist, The University of Western AustraliaShaun Collin, Winthrop Professor/WA Premier's Research Fellow, School of Animal Biology and the Oceans Institute, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/541202016-02-08T06:10:41Z2016-02-08T06:10:41ZRelax, shark numbers aren’t booming, but more research can make us safer<p>A documentary airing tonight on ABC’s Four Corners, “<a href="http://www.abc.net.au/4corners/stories/2016/02/04/4400419.htm">Shark Alarm</a>”, comes on the heels of a <a href="https://theconversation.com/state-of-fear-what-should-we-do-about-sharks-in-new-south-wales-47413">spate of shark bites in New South Wales</a> and raises questions about our relationship with these formidable animals. </p>
<p>Why do sharks bite humans? Are shark numbers “exploding”? If they are, is that a good or a bad thing? And the ultimate question (from a human point of view, at least): how can we make ocean users safer?</p>
<p>Anyone who says that they can confidently predict when, where or why sharks bite people is almost certainly wrong, regardless of whether they’re a scientist, a politician or a journalist. Why? Partly because we simply don’t know enough about sharks to anticipate their moves, and partly because attacks are <a href="https://theconversation.com/shark-bite-statistics-can-lie-and-the-result-is-bad-policy-21789">so rare</a>. Despite the media <a href="http://www.ncbi.nlm.nih.gov/pubmed/23110588">hype</a>, you’re still more likely to <a href="http://www.royallifesaving.com.au/__data/assets/pdf_file/0006/14559/RLS_NDR2015_Report_LR.pdf">drown</a> than be bitten by a shark.</p>
<p>The inconvenient truth is that ocean users may simply have to accept the risk of this very rare event, as unpalatable as that may be. But if that makes you uncomfortable, here are a few things to consider.</p>
<p>The shark population “explosion” cited as an explanation for the rise in attacks is very unlikely to be real. Within the animal kingdom, sharks are famously slow reproducers. Female great white sharks, for instance, typically produce a couple of offspring every other year, and only start reproducing <a href="http://www.iucnredlist.org/details/3855/0">once they reach 17 years of age</a>. The frilled shark <em>Chlamydoselachus anguineus</em> gestates for a period of <a href="http://www.wdc-jp.biz/pdf_store/isj/publication/pdf/37/373/37310.pdf">3.5 years</a>. </p>
<p>As a result, sharks are incapable of “baby booms” and indeed are very <a href="http://www.publish.csiro.au/paper/MF97135.htm">sensitive</a> to even low levels of fishing.
We may be seeing more sharks in some specific areas due to changes in ocean conditions, but rabbits they are not.</p>
<p>All of the scientific evidence points to declines rather than increases in the numbers of these animals, both <a href="http://www.dulvy.com/extinction-risk-and-conservation-of-the-worldrsquos-sharks-and-rays.html">globally</a> and in Australia’s own <a href="http://www.sciencedirect.com/science/article/pii/S0165783612001786">backyard</a>. The apparent uptick in shark bites is probably due to <a href="http://bit.ly/20E0RIq">more people in the water</a> rather than more sharks.</p>
<h2>More sharks doesn’t mean more bites</h2>
<p>What’s more, even if they were exploding in numbers, there is <a href="http://www2.hawaii.edu/%7Ecarlm/">no evidence</a> for a link between shark abundance and the likelihood that you will get bitten. Nor is there evidence that catching and killing sharks using drum lines – baited hooks attached to floating barrels – makes people safer, as demonstrated in Hawaii’s culling of <a href="https://scholarspace.manoa.hawaii.edu/handle/10125/2202">more than 4,000 sharks</a>. </p>
<p>So would fewer sharks be a good thing? No. A wealth of research shows that top predators like sharks are critical to ecosystem health, including protecting certain fisheries from <a href="http://science.sciencemag.org/content/315/5820/1846">collapse</a>, determining <a href="http://onlinelibrary.wiley.com/doi/10.1890/09-2174.1/abstract">where</a> and <a href="http://onlinelibrary.wiley.com/doi/10.1111/oik.01318/abstract">what</a> fish eat, when they <a href="http://www.int-res.com/articles/meps/203/m203p275.pdf">spawn</a>, how long they spend <a href="http://onlinelibrary.wiley.com/doi/10.1890/07-1671.1/abstract">hiding</a> in crevices, how deep they <a href="http://www.ncbi.nlm.nih.gov/pubmed/11809783">dive</a>, how “fat” or <a href="http://www.ncbi.nlm.nih.gov/pubmed/22380551">healthy</a> they are, and how fast they <a href="http://www.d.umn.edu/%7Ethrabik/Sogard%201997%20Bull%20Marine%20Sci.pdf">grow</a>. </p>
<p>What’s more, healthy shark populations may well mitigate against a range of ocean stressors including <a href="http://www.nature.com/nclimate/journal/v5/n12/full/nclimate2763.html">climate change</a>. In short, healthy oceans need healthy shark populations.</p>
<p>So much for healthy oceans – what about our own safety? Well that remains a challenge, and at the moment we’re going the wrong way about addressing it. The ground-breaking Harvard sociobiologist E. O. Wilson famously said: </p>
<blockquote>
<p>We are not afraid of predators, we’re transfixed by them, prone to weave stories and fables and chatter endlessly about them, because fascination creates preparedness, and preparedness, survival. In a deeply tribal way, we love our monsters…“</p>
</blockquote>
<p>To that end, knowledge is power. Destructive drum lines and nets don’t create preparedness because they don’t make us <a href="https://theconversation.com/has-queensland-really-saved-lives-by-killing-thousands-of-sharks-23437">safer</a> and they don’t help us <a href="https://theconversation.com/was-shark-cull-didnt-answer-the-big-ocean-safety-questions-26512">learn</a>. Insidiously, they make us feel safer even though we may not be, potentially leading us to enter the water with far less vigilance than we ought to have. </p>
<p>Shark bites have been happening for centuries, but we are still stuck in a Groundhog Day mindset, reacting rather than learning. We need to shift the paradigm and approach the problem with open minds. A big part of this will involve developing an understanding of where and when shark bites occur and how this relates to our use of the oceans. </p>
<p>Investing in research is arguably the best way to prepare. Recent research from James Cook University has <a href="http://www.abc.net.au/news/2016-02-04/great-barrier-reef-bull-sharks-secret-lives-revealed/7136950">generated insights</a> into the "secret lives” of bull sharks, as has <a href="http://www.swellnet.com/news/swellnet-dispatch/2015/03/03/australias-white-shark-population-hunt-answers">research on white shark movements and abundance by CSIRO</a>. </p>
<p>Globally, <a href="http://science.sciencemag.org/content/348/6240/1255642.full?ijkey=MM1HJF8PtdZz.&keytype=ref&siteid=sci">tagging studies</a> and projects such as South Africa’s <a href="http://sharkspotters.org.za">Shark Spotter</a> program have taught us much about shark behaviours and movements, which will be critical to reducing human risk. <a href="http://onlinelibrary.wiley.com/doi/10.1111/brv.12246/abstract">Non-destructive sampling</a> will be crucial to understanding the abundance and distribution of these animals as we assess their conservation status.</p>
<p>To that end, the New South Wales state government’s <a href="http://www.abc.net.au/news/2015-08-14/nsw-launches-shark-tagging-surveillance-in-wake-of-attacks/6696392">decision</a> to invest in new technologies that generate knowledge, rather than simply killing more animals, should be applauded. Our challenge as a nation is to now move beyond crude drum lines and nets that kill sharks and other marine wildlife, and to give that funding instead to programs that help us love our monsters … through knowledge, not fear.</p><img src="https://counter.theconversation.com/content/54120/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The best way to guard against shark attacks is to study them, not kill them. Because while the alleged “shark boom” almost certainly not real, the more we know about sharks, the better.Jessica Meeuwig, Professor & Director, Centre for Marine Futures, The University of Western AustraliaLaurie Laurenson, Associate Professor, School of Life and Environmental Sciences, Deakin UniversityShanta Barley, PhD candidate, School of Animal Biology, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/531642016-01-24T19:35:59Z2016-01-24T19:35:59ZGiant monster Megalodon sharks lurking in our oceans: be serious!<figure><img src="https://images.theconversation.com/files/108923/original/image-20160122-9763-1vkufe3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An artist's impression of the giant shark, megalodon.</span> <span class="attribution"><span class="source">Shutterstock/Catmando</span></span></figcaption></figure><p>The sighting of a seven-metre shark off the South Australia coast this month has excited the <a href="http://www.dailymail.co.uk/news/article-3404180/Huge-SEVEN-metre-Great-White-shark-branded-biggest-spotted-just-100-metres-offshore-lifesaving-helicopter.html">world’s media</a> with some <a href="http://www.dailystar.co.uk/news/latest-news/488428/Swimmers-flee-seven-metre-Great-White-Shark-off-coast">making reference</a> to the great white that featured in the classic 1975 film <a href="http://www.imdb.com/title/tt0073195/">Jaws</a>.</p>
<p>It was certainly a big shark but there are tales of even bigger sharks lurking in our waters. A quick <a href="https://www.google.com.au/search?q=Megalodon">Google search</a> on “megalodon” brings up around 1.2 million hits about this monster prehistoric shark, made famous in the 2002 eponymous <a href="http://www.imdb.com/title/tt0284303/">B-movie</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/cQGa5joOPno?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Web pages feature frightening <a href="https://www.youtube.com/watch?v=6aKcazsEWPk">movie clips</a> claiming to show evidence that this gigantic fossil shark, once reaching around 17m in length, is still alive out there, perhaps living in deep seas where they escape detection.</p>
<p>Megalodon (meaning “big tooth”) is really the vernacular name used for <em>Carcharocles megalodon</em>, an extinct relative of today’s great white and mako sharks in the family Lamnidae. Megalodon is known from its huge fossil teeth, the largest being 18 centimetres long, found nearly all around the globe in fossil marine deposits. It lived from about 16 million to 2.6 million years ago. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/108366/original/image-20160117-20954-mqklb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/108366/original/image-20160117-20954-mqklb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108366/original/image-20160117-20954-mqklb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=615&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108366/original/image-20160117-20954-mqklb4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=615&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108366/original/image-20160117-20954-mqklb4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=615&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108366/original/image-20160117-20954-mqklb4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=773&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108366/original/image-20160117-20954-mqklb4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=773&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108366/original/image-20160117-20954-mqklb4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=773&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Reconstructed jaws of <em>Carcharocles megalodon</em> by the American Museum of Natural History, New York. This 1927 reconstruction is now thought to be about 30% too big, based on what we know about the teeth, but gives a good idea of the monstrous size of this shark.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Carcharodon_megalodon.jpg">Wikimedia</a></span>
</figcaption>
</figure>
<p>The recent Discovery Channel <a href="http://www.imdb.com/title/tt3100780/">mockumentary</a> about megalodon still being alive had a short disclaimer that it was fictional. Nonetheless, it seems to have sparked a lot of subsequent interest in whether or not such a shark could really out there.</p>
<p>Several articles have been <a href="http://blog.oceans-campus.com/blog/bid/394525/Megalodon-Debunking-the-myths">written</a> with shark experts debunking these myths. So where did the stories of megalodon’s survival originate from, and what is the truth behind these claims? </p>
<h2>Great White sharks – the big one that got away</h2>
<p>Perhaps the first case of megalodon mania sprung from real published records of a monster great white in an esteemed museum collection. The largest living predatory shark today, <a href="http://australianmuseum.net.au/white-shark-carcharodon-carcharias-linnaeus-1758">the great white shark</a>(<em>Carcharodon carcharias</em>) grows up to around 6.4m, based on a shark caught off Cuba in 1964.</p>
<p>Early records in the published scientific literature speak of an 11-metre giant caught of Port Fairy, Victoria in the 1860s. The jaws of this fish were sent to the collections of the British Museum of Natural History, in London. The calculated size of the fish was published in the book <a href="http://catalogue.nla.gov.au/Record/2649050">Catalogue of Fishes</a> of the museum by Albert Günther, Keeper of Zoology at the museum in 1870. </p>
<p>But in the 1970s, American ichthyologist <a href="http://australianmuseum.net.au/image/dr-john-e-randall">John Randall</a> doubted this measurement and so he visited the museum in London to recalculate the body size. The original jaws that Gunther studied were examined and their measurements plotted against other specimens where accurate body length to jaw size was known.</p>
<p>Randall’s new calculation of the Port Fairy specimen was approximately five metres in length, within typical great white body size range. Randall suggested that a typo crept into the original publication where it should have read 16.5 feet but instead stated 36.5 feet.</p>
<p>Strangely, it was not picked up in the second edition of the book in which Günther added a maximum size of the shark being 40 feet (12.2m). These inaccurate size estimates published in such a scientifically respectable book no doubt fuelled the idea that monster great whites really did exist in modern times.</p>
<p>One last bit of relevant information about just how big great whites might grow comes from a report of measured bite marks on a whale carcass off Albany during the last decade of whaling in Western Australia.</p>
<p>Back in the mid-1970s, <a href="https://au.news.yahoo.com/thewest/wa/a/28674912/colin-ostle-veteran-shark-hunter-predicts-more-attacks/">Colin Ostle</a> was employed by the department of fisheries, and his job was to measure the whale carcasses that were taken by the whaling company.</p>
<p>I spoke with Colin and he told me how he also routinely measured shark bite marks on whale carcasses and recorded them in his notebook. Over a seven-year period he also caught around 60 great whites, so he was very familiar with their behaviour.</p>
<p>The largest jaw bite marks he ever recorded measured 19x24 inches as part of five bites, all made by the same very large shark which attacked a floating sperm whale carcass that had broken free of its chain as it was towed in to the harbour.</p>
<p>When compared to a 16-foot shark (4.87m) with a known bite gape of 11x13 inches, the scaling up of these large bites would suggest a shark up to 7.8m in length was then alive in the seas off Albany. In 1968, even larger shark bites were claimed to be observed on a whale carcass, but measurements were not recorded.</p>
<p>Shark ecologist <a href="http://www.flinders.edu.au/people/charlie.huveneers">Dr Charlie Huveneers</a> of Flinders University is cautious about extrapolating absolute size from bite marks, but conceded to me that:</p>
<blockquote>
<p>[…] it is quite conceivable that sharks larger than the scientifically confirmed maximum size exist, as for most species scientists are unlikely to have measured the largest individual of that species.</p>
</blockquote>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/108487/original/image-20160119-31834-sasudh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/108487/original/image-20160119-31834-sasudh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108487/original/image-20160119-31834-sasudh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=453&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108487/original/image-20160119-31834-sasudh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=453&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108487/original/image-20160119-31834-sasudh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=453&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108487/original/image-20160119-31834-sasudh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=569&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108487/original/image-20160119-31834-sasudh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=569&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108487/original/image-20160119-31834-sasudh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=569&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Woodcut from Niels Stensen’s 1667 monograph on the dissection of a great white shark. Megalodon teeth are pictured at right. Stensen identified them as sharks teeth rather than fossilised tongue stones.</span>
</figcaption>
</figure>
<h2>New research about Megalodon and its demise</h2>
<p>Around 400 years ago, megalodon teeth were thought to be petrified tongues. In 1667, the Danish anatomist <a href="http://evolution.berkeley.edu/evolibrary/article/history_04">Nicolas Steno</a> figured out from his dissection of a great white shark head that they were the teeth of ancient large sharks.</p>
<p>Scaling up teeth and jaw size with known living sharks yields an approximate maximum size for megalodon around 17m. But, in weight, it would have been at least ten times the mass of a large great white shark.</p>
<p>Unlike great whites, we deduce that megalodon targeted large baleen whales as its prime prey, as we have found its <a href="http://phys.org/news/2011-11-ancient-shark-fossil-whale-bone.html">tooth marks on fossil whale bones</a> and sometimes <a href="http://www.bioone.org/doi/full/10.2110/palo.2008.p08-077r">teeth stuck into whale fossils</a>. Some of these specimens can also be put down to scavenging behaviour.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/108680/original/image-20160120-26105-1t4ap52.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/108680/original/image-20160120-26105-1t4ap52.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108680/original/image-20160120-26105-1t4ap52.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=433&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108680/original/image-20160120-26105-1t4ap52.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=433&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108680/original/image-20160120-26105-1t4ap52.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=433&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108680/original/image-20160120-26105-1t4ap52.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=544&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108680/original/image-20160120-26105-1t4ap52.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=544&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108680/original/image-20160120-26105-1t4ap52.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=544&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A large m tooth from California measuring close to 15cm. The largest tooth ever measured was just over 18cm, suggesting a maximum body length of up to 17m for this shark.</span>
<span class="attribution"><span class="source">J Long, Flinders University</span></span>
</figcaption>
</figure>
<p>In recent years several scientific papers by <a href="https://www.researchgate.net/profile/Catalina_Pimiento">Dr Catalina Pimiento</a>, of the Florida Museum of Natural History, have greatly elucidated our knowledge about this impressive prehistoric predator. Her <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4541548/">study calculating its trends in body size</a> through time show its average size was likely around 10m for most of its 14-million year reign.</p>
<p>We know that its raised its young (starting at 2m length) <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0010552">in nursery areas</a> of the eastern Pacific. <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0111086">Another study</a> confirms that the species died out at least 2.6 million years ago, based on many reliably dated fossil sites.</p>
<p>Pimiento suggests that the the modern baleen whale fauna was probably established after the extinction of megalodons. </p>
<p>The reasons for megalodons demise are unknown, but could relate to either climate change or biological factors, like the events concerning the evolution and migration of whales to colder Antarctic waters where the sharks could not go.</p>
<p>I proposed this idea back in 1995 in the first edition of my book <a href="https://jhupbooks.press.jhu.edu/content/rise-fishes">The Rise of Fishes</a>. Dr Pimiento’s new research currently in press seems to support the view. She told me:</p>
<blockquote>
<p>I found no evidence for a relationship between megalodon distribution and climate, and therefore, no support for such hypotheses. Instead, I found that megalodon trends in distribution coincide with diversification events in marine mammals and in other sharks, further supporting the biotic set of hypotheses.</p>
</blockquote>
<p>It seems likely that the growth and huge size of modern baleen whales, the largest animals on the planet, could well have been driven by predation pressures from megalodons.</p>
<p>Their ability to endure and feed in near freezing Antarctic waters might have been a key reason why megalodons went extinct. Thankfully, for all of us who love swimming and diving in the sea.</p><img src="https://counter.theconversation.com/content/53164/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Long receives funding from The Australian Research Council. </span></em></p>Giant sharks did once exist in our oceans – many millions of years ago. But rumours persist that some may still be alive today.John Long, Strategic Professor in Palaeontology, Flinders UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/533992016-01-20T13:28:02Z2016-01-20T13:28:02ZThe science behind that ‘Jaws’ sighting – and why it’s cause for celebration<p>It was, by any measure, a giant. On January 17, patrol helicopters off the coast of southern Australia reported seeing a <a href="http://www.smh.com.au/environment/animals/great-white-shark-up-to-7m-long-sighted-off-south-australian-beach-20160118-gm81yw.html">great white shark “nearly as big as Jaws”</a>. In fact, it was estimated to be up to <a href="http://www.telegraph.co.uk/news/worldnews/australiaandthepacific/australia/12105642/Australian-beach-evacuated-after-shark-as-big-as-Jaws-spotted.html">23ft long</a>, only marginally smaller than the infamous <a href="http://www.imdb.com/title/tt0073195/">movie killer</a> – and it came to within just <a href="https://www.facebook.com/532506756862271/photos/a.581113098668303.1073741828.532506756862271/871385016307775/?type=3&theater">100 metres of the shore</a>. Perhaps unsurprisingly, the connotations with Peter Benchley’s 1974 novel sent the internet into its usual frenzied panic when such a “monster” is spotted. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/108743/original/image-20160120-26082-14696fb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108743/original/image-20160120-26082-14696fb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=551&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108743/original/image-20160120-26082-14696fb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=551&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108743/original/image-20160120-26082-14696fb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=551&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108743/original/image-20160120-26082-14696fb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=692&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108743/original/image-20160120-26082-14696fb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=692&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108743/original/image-20160120-26082-14696fb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=692&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">One of the images of the giant shark posted on Facebook by Shark Alerts South Australia.</span>
<span class="attribution"><a class="source" href="https://www.facebook.com/532506756862271/photos/a.581113098668303.1073741828.532506756862271/871385016307775/?type=3&theater">Shark Alerts South Australia/Facebook</a></span>
</figcaption>
</figure>
<p>Last summer, videos of what many believe to be the largest white shark ever caught on film also sent the internet into <a href="http://news.nationalgeographic.com/2015/08/150814-sharks-great-whites-animals-science-biggest/">meltdown</a>. These large sharks will always make headlines, but instead of igniting fear, they should be cause for celebration. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/OjWsy2DwGRU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>In recent years, many sharks – including the great white – have been severely reduced in numbers, with some species down by 90%. While calculating the precise numbers of individuals is difficult, there are promising signs that some white shark <a href="https://theconversation.com/white-shark-populations-are-growing-heres-why-thats-good-news-44872">populations are now on the rebound</a>. This is in part due to measures put in place to protect both the <a href="https://theconversation.com/white-shark-populations-are-growing-heres-why-thats-good-news-44872">sharks and their main prey</a>, marine mammals.</p>
<p>The sharks have either been killed by targeted commercial fishing for their fins and meat, or accidentally caught in other fisheries. Elsewhere, they are hunted for trophies, grandstanding profile pictures or because they are seen as a threat to humans. It has been estimated that between <a href="http://www.sciencedirect.com/science/article/pii/S0308597X13000055">63m and 273m sharks could be killed every year</a> by fishing. Populations have reached such low numbers in places <a href="http://elifesciences.org/content/3/e00590">that some species now are at a high risk of extinction</a>. </p>
<p>Which makes the latest sighting very special indeed. At a time when many species are struggling, such a large shark is a rare sight. </p>
<h2>So how big was it?</h2>
<p>There is a famous tendency to exaggerate the size of fish – and sharks, in particular. The referenceless of the ocean can make judging distances and length difficult and with no solid means to verify the size of this shark, we can’t say for sure that it really was seven metres long. While coast guards reported that the shark was <a href="https://www.facebook.com/532506756862271/photos/pb.532506756862271.-2207520000.1453287722./871385016307775/?type=3&theater">bigger than their six-metre jet boat</a>, it is hard to extract any biologically relevant information from the fleeting sighting other than it was a big shark doing what sharks do. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/108561/original/image-20160119-29790-18hl1ra.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108561/original/image-20160119-29790-18hl1ra.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108561/original/image-20160119-29790-18hl1ra.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108561/original/image-20160119-29790-18hl1ra.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108561/original/image-20160119-29790-18hl1ra.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108561/original/image-20160119-29790-18hl1ra.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108561/original/image-20160119-29790-18hl1ra.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A graceful giant.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/elevy/14730744390/in/photolist-orGV6y-oHVQbc-oJawSh-g7GM-oHVAYR-jU2Tsg-2dhHx-wfSUHR-oGayXL-oGaLLW-oJaEnh-oGaMs5-orGNVX-oHVAJT-orHm8z-orHiFR-QMsXq-oJaDoJ-os5Wna-oGaJij-orGGua-cCQ7M-sbDxoo-u8wL-orHgL8-cJbwW7-cvGkT7-cJbx79-orHbye-6Xrbg1-9cKZn3-AFtTKM-66vQdC-2dhHw-4EReGw-4ERf6h-nnRB1t-uFXbpz-fbMVok-dLuyfN-dLuyao-dLuydb-2cPKa1-2T2yzM-QNsJK-6hosY1-mH2d1-ewpTU8-4ERehu-um4tBf">Elias Levy/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>What we can say, however, is that large great white sharks are usually the old ones. And they can get really quite old. In fact, a recent study found that white sharks might live <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0084006">as long as 70 years</a>. These older sharks are great for the population, because they have had ample opportunity to reproduce, introducing offspring into a dwindling population. </p>
<p>But in all the Jaws-style fanfare, it’s important to look also at how the local community has dealt with the sighting. In many places around the world, just as in the film Jaws, we might <a href="https://www.thedodo.com/shark-catch-kill-attack-wa-905275136.html">have seen a large-scale hunt undertaken</a> to capture the “man-eating” monster and stop it from killing on their beaches. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/U1fu_sA7XhE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>The hunted hunter</h2>
<p>Indeed, Western Australia recently controversially lifted the protective status of great white sharks and implemented a shark cull along its coast in an attempt to boost tourism after a spate of fatal shark incidents. But the programme came under huge criticism for failing to capture a <a href="https://theconversation.com/five-take-home-messages-from-was-official-shark-cull-numbers-26381">single white shark</a> and killing many other species not involved in recent fatalities. </p>
<p>Destroying sharks to increase beach safety has been widely <a href="https://theconversation.com/why-were-opposing-western-australias-shark-cull-scientists-28653">criticised by the scientific community</a> due to the huge impact that these methods can have on many aspects of the ecosystem. In the past, countless technologies and protocols were developed to reduce the number of fatalities from shark incidents, but with no unifying answer. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/108560/original/image-20160119-29790-qksccd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108560/original/image-20160119-29790-qksccd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=395&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108560/original/image-20160119-29790-qksccd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=395&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108560/original/image-20160119-29790-qksccd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=395&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108560/original/image-20160119-29790-qksccd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=496&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108560/original/image-20160119-29790-qksccd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=496&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108560/original/image-20160119-29790-qksccd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=496&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Taking the bait.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/lwpkommunikacio/14663970488/in/photolist-okNFxo-poTVwD-bLgd38-okP83k-oC2r7v-oJwJVe-poQQmM-oJtPBf-oJtMQj-pFkhdR-poQRfa-poTeAY-pF6vLg-poVTNC-oJtN1E-pFpxcY-poTerE-zpdVy-cnUiJ3-zojko-EAjjx-97nAbR-cnUh33-gLftrs-pbwoVf-2dhHy-8aijQr-ewnXxT-8WiwtP-cJbsuL-oHVLa6-oHVMP8-4ugKm7-cJbBPq-bHubUR-8aim6M-oHVPJR-i8xKL-orGV6y-cnUmnh-cnUkz3-cnUi4A-cnUjQd-cmdEL9-9wd3mZ-DBKfK-68nKsp-orH1pY-oHVQbc-g7GM">Lwp Kommunikáció/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>But the latest sighting offers fresh hope. What we have here is a community that is learning to share the ocean with these important ocean predators. <a href="https://www.facebook.com/Shark-Alerts-South-Australia-532506756862271/">Shark Alerts South Australia (SASA)</a>, the Facebook page where the initial sighting was shared, is emblematic of a community accepting the beauty and significance of the great white. </p>
<p>Following the sighting, local ocean events were cancelled and “shark sirens” were sounded. But while ocean users exited the waters, helicopters and boats were deployed not to kill, but to herd “the large white shark out to sea”. All the while <a href="https://www.facebook.com/Shark-Alerts-South-Australia-532506756862271/">SASA</a> were sharing the information with its 55,000+ followers. </p>
<p>The community driven <a href="https://www.facebook.com/Shark-Alerts-South-Australia-532506756862271/">Facebook page</a> is updated regularly and allows potential users to think twice before entering potentially dangerous situations. Last year they reported about 170 to 180 sightings, but as their followers continue to increase, so will their reports. This is a great example of how social media and advances in technology can help reduce the number of incidents, while educating people at the same time. </p>
<h2>Age of the technoshark</h2>
<p>In Western Australia, tagged sharks are now “using” Twitter to alert ocean users to their presence near local beaches. And in the scientific world, new technologies and autonomous underwater drones are being used to <a href="http://onlinelibrary.wiley.com/doi/10.1111/jfb.12828/abstract">observe previously unseen habitats</a>, feeding ecology and behaviors in great white sharks. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"689228930079850496"}"></div></p>
<p>It has been found that many ocean users in Australia often encounter sharks, without harm, and <a href="http://www.sciencedirect.com/science/article/pii/S0308597X15000962">support further research and education</a>. These are all promising signs that we are moving away from the barbaric approaches to mitigating shark incidents. Instead, communities are learning to share the ocean with sharks, even profiting from <a href="http://www.sciencedirect.com/science/article/pii/S0025326X14008054">tourism industries set up specifically to see them</a>. </p>
<p>Sharks are hugely important for maintaining the balance and health of our ecosystems. Learning to live alongside them will be challenging and we still have a long way to go. But with changing perceptions and advances in technology, a peaceful coexistence with “Jaws” may be closer than you think.</p><img src="https://counter.theconversation.com/content/53399/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christopher Bird does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>How new technologies and changing attitudes are enabling people and great whites to live together.Christopher Bird, Ph.D student: Shark Ecology, University of SouthamptonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/525482015-12-22T05:21:19Z2015-12-22T05:21:19ZFour useful tips on how to be shark smart this summer<figure><img src="https://images.theconversation.com/files/106636/original/image-20151218-27854-pb46rj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Choosing to swim or surf at a beach with shark spotters or lifeguards may save you a limb or your life.</span> <span class="attribution"><span class="source">Glencairn Leigh de Necker</span></span></figcaption></figure><p>Summer is the time many people head to the beach to enjoy a refreshing dip in the sea to wash away the years’ hard work. Being bitten by a shark remains a concern for many beachgoers even though statistically, the chances are extremely <a href="https://www.flmnh.ufl.edu/fish/sharks/isaf/2014Summary.html">low.</a></p>
<p>Last year, worldwide 72 people were bitten in unprovoked incidents with three <a href="https://www.flmnh.ufl.edu/fish/sharks/statistics/statsw.htm">deaths</a>. In South Africa this year, five people have been bitten by a shark with no fatalities.</p>
<p>Of the more than 500 species of <a href="http://www.sharksider.com/">shark</a>, only the great <a href="http://animals.nationalgeographic.com/animals/fish/great-white-shark/">white</a>, <a href="http://animals.nationalgeographic.com/animals/fish/bull-shark/">bull</a> (Zambezi) and tiger <a href="http://animals.nationalgeographic.com/animals/fish/tiger-shark/">shark</a>, pose a significant threat to humans. All three of these species occur in waters off Africa.</p>
<p>So, here are four shark safety tips you can use to avoid being bitten by one of them.</p>
<h2>Stay close to lifeguards and shark spotters</h2>
<p>Ocean surveillance is one of the best ways to make sure the paths of people and sharks do not overlap. While using the ocean is always at your own risk, life guards or organisations like <a href="http://sharkspotters.org.za/">Shark Spotters</a> provide extra security by giving relevant warnings and assisting in the event of an emergency. </p>
<p>Always obey beach officials, lifeguards and shark spotters if told to leave the water. And first-time visitors should ask them about the area before heading in. Always pay attention to shark signage on beaches.</p>
<h2>Avoid shark hunting grounds</h2>
<p>Do not swim, surf or surf-ski when lots of birds, dolphins or seals are feeding nearby. This activity suggests there are schools of baitfish and other predators, like sharks, in the area. Along the same lines, avoid areas where trek-netting, fishing or spear fishing is taking place because sharks, just like the fishermen, are attracted to the fish. Dead whales are like a giant magnet for sharks, so do not swim, surf or surf-ski if there’s a whale stranding nearby.</p>
<p>Sharks, like lions, are ambush predators and use their habitat to their advantage. They like to hunt near deep water channels next to drop-offs and kelp forests. They also use low light like dawn and dusk and murky water to hide in, and sneak up on their prey.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/106637/original/image-20151218-27875-ozlg4q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/106637/original/image-20151218-27875-ozlg4q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/106637/original/image-20151218-27875-ozlg4q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=395&fit=crop&dpr=1 600w, https://images.theconversation.com/files/106637/original/image-20151218-27875-ozlg4q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=395&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/106637/original/image-20151218-27875-ozlg4q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=395&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/106637/original/image-20151218-27875-ozlg4q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=496&fit=crop&dpr=1 754w, https://images.theconversation.com/files/106637/original/image-20151218-27875-ozlg4q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=496&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/106637/original/image-20151218-27875-ozlg4q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=496&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sharks hunt near deep water channels, they can attack their prey in murky water and use low light to hide in and sneak up on their prey.</span>
<span class="attribution"><span class="source">Morne Hardenberg</span></span>
</figcaption>
</figure>
<p>River mouths are another place sharks like to feed near because they are so attractive to fish and often water visibility is very poor which is to the sharks’ advantage.</p>
<h2>Don’t swim solo</h2>
<p>You are vulnerable on your own and there is safety in numbers. The more people in the water with you, the more chance of spotting sharks and having someone close by to lend a hand in case of an emergency. If you are kayaking or surf-skiing far out to the sea, consider paddling in groups and staying close together.</p>
<p>If you really must be on your own, think about using an electronic shark repellent. Although there is no shark deterrent on the market that guarantees your safety 100%, the <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0062730">Shark Shield</a>, has proved effective in some scenarios. If you are surfing, kayaking, diving or spearfishing in areas where encountering a shark is likely, then this is a good option to consider.</p>
<h2>Don’t set yourself up as competition</h2>
<p>Sharks have acute senses, especially smell. So if you are diving for crayfish do not use a bait bag and similarly, if you spearfish, do not carry your fish with you as this will attract the attention of sharks close by and you may find yourself in competition with a large shark.</p>
<p>Always remember that the ocean is a wild space with wild creatures, which means there are no 100% guarantees. But the risk of being bitten by a shark can be lowered if people exercise caution and are aware of their environment.</p><img src="https://counter.theconversation.com/content/52548/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alison Kock works for Shark Spotters. She receives funding from the Save Our Seas Foundation, Two Oceans Aquarium and the University of Cape Town. She is affiliated with the South African Shark Conservancy, University of Cape Town and South African Institute of Aquatic Biodiversity.</span></em></p>Despite low shark attack numbers, many people are afraid of being bitten. There are, however, ways to steer clear of these creatures.Alison Kock, Research Manager, Shark Spotters and Honorary Research Associate, South African Institute for Aquatic BiodiversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/507922015-11-30T04:35:34Z2015-11-30T04:35:34ZLow levels of genetic diversity are putting great white sharks at risk<figure><img src="https://images.theconversation.com/files/102994/original/image-20151124-18271-1w5726q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Great white sharks in South Africa have extremely low genetic diversity compared with shark populations elsewhere in the world.</span> <span class="attribution"><span class="source">Sara Andreotti/www.sharkdivingunlimited.com</span></span></figcaption></figure><p>Despite international protection, great white sharks face several <a href="http://www.iucnredlist.org/details/3855/0">threats</a>. These include reduction of their food supply, pollution, baited hooks and lethal gill nets used as beach protection measures.</p>
<p>The cryptic nature of white sharks makes them challenging to study. And it is difficult to protect a species we don’t know much about. But new <a href="http://onlinelibrary.wiley.com/doi/10.1111/jbi.12641/abstract">research</a> has now added another piece of the puzzle towards understanding these creatures.</p>
<p>Research on the DNA of white sharks around the South African coastline shows that the population has extremely low genetic <a href="http://onlinelibrary.wiley.com/doi/10.1111/jbi.12641/abstract">diversity</a>. This finding holds serious implications for their survival and more analysis is being done to try and understand this unexpected outcome and predict its consequences for the future of the species.</p>
<h2>What genetic diversity tells us</h2>
<p>Genetic diversity is an important indicator of the health status of a population in the <a href="https://www.researchgate.net/profile/Richard_Frankham/publication/228740794_Correlation_between_fitness_and_genetic_diversity/links/09e41511350bd93ea9000000.pdf">wild</a>: the higher the diversity, the easier it is for a species to survive diseases or unexpected changes in the environment. Among genetically different individuals there will always be those able to adapt and contribute to the next generation.</p>
<p>A different scenario emerges when all the individuals share the same genetic information since depression by inbreeding and the loss of ability to adjust to environmental changes can quickly lead a species to <a href="http://webpages.icav.up.pt/ptdc/BIA-BEC/099934/2008/papers/Frankham_2005_Biological_Conservation.pdf">extinction</a>.</p>
<p>We found only four maternally inherited lineages in the South African great white population, with 89% of all the sharks sharing the exact same lineage. Both mitochondrial and microsatellites data sets showed a remarkably low level of genetic diversity.</p>
<p>The data on the mitochondrial DNA suggests that great whites off South Africa’s coastline have the lowest genetic diversity of any white shark population in the world. Even lower than the Black Sea’s endangered bottlenose dolphin when compared with other marine <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1564106/">species</a>.</p>
<p>The reasons for this low level of genetic diversity could include:</p>
<ul>
<li><p>the result of a severe bottleneck: a sharp reduction in the population size due to environmental factors.</p></li>
<li><p>historical local extinction: when a population ceases to exist in the chosen geographic area of study but still exists elsewhere.</p></li>
<li><p>extinction/re-colonization processes: this sees locally extinct species from a chosen geographic area return thanks to immigration.</p></li>
</ul>
<h2>Why DNA is important</h2>
<p>The analyses of DNA is an incredibly useful tool when dealing with an elusive species. Every historical migration and reduction or expansion of a population is kept as a record in the DNA.</p>
<p>An analogy would be the way in which the captain of a ship keeps track of a ship movements in its logbook. In the DNA logbook several chapters can be studied. Some of them tell the ancient story of the female lineages - mitochondrial DNA. Some describe the most recent history of the population movements or even the family <a href="https://dendrome.ucdavis.edu/ctgn/files/Vol_05_print.pdf">trees</a>- microsatellite analyses.</p>
<p>We performed both mitochondrial and microsatellite analyses on samples collected around the South Africa’s coastline. We sailed on a research catamaran for four years, attracting sharks, identifying them by taking pictures of their dorsal fins and collecting genetic samples.</p>
<p>The DNA of the South African white sharks was then compared with the DNA of 58 white sharks worldwide from <a href="http://www.researchgate.net/profile/Dean_Blower/publication/272820161_Population_genetics_of_Australian_white_sharks_reveals_fine-scale_spatial_structure_transoceanic_dispersal_events_and_low_effective_population_sizes/links/54efb7560cf2495330e286eb.pdf">studies</a> conducted elsewhere. This helped us determine the genetic diversity and population distribution of the South African great whites compared with others across the world.</p>
<p>The study shows that South African white sharks belong to one interbreeding population. Some of the sharks identified in the south-west coast’s False Bay have been re-sighted on the east coast’s Algoa Bay. This finding has important implications for environmental management of the population.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/102995/original/image-20151124-18246-12f074s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/102995/original/image-20151124-18246-12f074s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/102995/original/image-20151124-18246-12f074s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=387&fit=crop&dpr=1 600w, https://images.theconversation.com/files/102995/original/image-20151124-18246-12f074s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=387&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/102995/original/image-20151124-18246-12f074s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=387&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/102995/original/image-20151124-18246-12f074s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=486&fit=crop&dpr=1 754w, https://images.theconversation.com/files/102995/original/image-20151124-18246-12f074s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=486&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/102995/original/image-20151124-18246-12f074s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=486&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Capturing the DNA of the Great White Shark.</span>
<span class="attribution"><span class="source">Gotz Froeschke</span></span>
</figcaption>
</figure>
<h2>Global connections</h2>
<p>The global connections of white shark populations are complex, reflecting a combination of many historical events shaping a species with more than 14 million years of <a href="http://www.tandfonline.com/doi/abs/10.1671/0272-4634%282001%29021%5B0730:AASOCA%5D2.0.CO;2">evolution</a>.</p>
<p>This includes the closure of the Isthmus of <a href="http://gsabulletin.gsapubs.org/content/104/7/814.short">Panama</a>, the narrow strip of land that separated the once connected Atlantic and Pacific Oceans 3.5 millions year ago. Other events, even if isolated, contributed to shape the complex distribution of white sharks population, like the infrequent long-distance migrations that originated in the Mediterranean <a href="http://rspb.royalsocietypublishing.org/content/early/2010/11/16/rspb.2010.1856.short">population</a>.</p>
<p>Our study provided further evidence that the modern all white sharks populations originated from an ancestral Indo-Pacific Ocean population and became slowly genetically distinct following a west to east migration pattern. They dispersed in the Atlantic through the once open Isthmus of Panama and then down to <a href="http://onlinelibrary.wiley.com/doi/10.1111/jbi.12641/abstract">South Africa</a>. Interestingly some sharks closely related to South African sharks have been sampled in Australia, but never the other way around.</p>
<p>Globally, the population of white sharks fall into three major <a href="http://onlinelibrary.wiley.com/doi/10.1111/jbi.12641/abstract">groups</a>: </p>
<ol>
<li>The Mediterranean and Indo-Pacific Oceans (Australia and California), </li>
<li>The North West Atlantic (Florida) and Indian Ocean (South Africa), and </li>
<li>A single divergent group restricted to South Africa only. </li>
</ol>
<p>The divergent South African group interestingly doesn’t connect with any other population sampled to date. The reason for this distinct divergence from the other two groups is currently unknown.</p>
<p>There is still a lot to understand about white sharks before effective conservation measures can be put in action. We still don’t know how long they live, where their nursery areas are or even exactly how many there are and how many get killed every year. </p>
<p>Based on the genetic results of this study we can only conclude that the low levels of genetic diversity would prevent this species from recovering quickly to a healthier population status. Population genetic theories predict that depletion in genetic diversity causes a reduction in the population’s ability to reproduce successfully. This will inevitably result in a reduction of <a href="https://www.researchgate.net/profile/Richard_Frankham/publication/228740794_Correlation_between_fitness_and_genetic_diversity/links/09e41511350bd93ea9000000.pdf">numbers.</a></p>
<p>In addition, white sharks reproduce slowly since they are not supposed to have any predators.</p>
<p>Besides their own survival, white sharks play an extremely important role in the ecosystem. Their extinction would negatively affect the entire ocean.</p><img src="https://counter.theconversation.com/content/50792/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sara Andreotti received funding for the field work, the vessels and logistical assistance by Michael Rutzen's Shark Diving Unlimited (<a href="http://www.sharkdivingunlimited.com">www.sharkdivingunlimited.com</a>).
Dr Andreotti was also financed by the Department of
Botany and Zoology Postgraduate Bursary Scheme and lab
work was funded through NRF incentive funding to Prof. Conrad A. Matthee</span></em></p>South African sharks have low levels of genetic diversity. This could pose a threat to their survival as a species.Sara Andreotti, Post-doctoral researcher in management and conservation of white sharks, Stellenbosch UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/451692015-08-04T04:42:41Z2015-08-04T04:42:41ZShark safety tips: sorting out fact from fiction<figure><img src="https://images.theconversation.com/files/90661/original/image-20150803-5998-nhmz7e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">There are certain times and locations where people are more likely to encounter a shark.</span> <span class="attribution"><span class="source">Morne Hardenberg</span></span></figcaption></figure><p>There are more than 500 species of shark and only three of them pose a significant threat to <a href="http://www.sharkinfo.ch/SI1_99e/attacks2.html">humans</a>. These are the great white, bull or Zambezi and tiger shark.</p>
<p>The probability of being bitten by a shark is statistically extremely low. There were 72 shark bites, three of them fatal, reported worldwide in <a href="http://www.businessinsider.com/r-fewer-shark-bites-in-2014-but-florida-still-tops-for-attacks-2015-2">2014</a>. Considering that hundreds of thousands of people use the ocean daily for recreation, this is a staggeringly low number.</p>
<p>There is a list of shark safety tips to follow that will reduce your individual risk even further. But have you ever wondered where the advice comes from and how to use it? </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/90613/original/image-20150803-6008-iyj9ka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/90613/original/image-20150803-6008-iyj9ka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/90613/original/image-20150803-6008-iyj9ka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=896&fit=crop&dpr=1 600w, https://images.theconversation.com/files/90613/original/image-20150803-6008-iyj9ka.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=896&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/90613/original/image-20150803-6008-iyj9ka.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=896&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/90613/original/image-20150803-6008-iyj9ka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1126&fit=crop&dpr=1 754w, https://images.theconversation.com/files/90613/original/image-20150803-6008-iyj9ka.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1126&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/90613/original/image-20150803-6008-iyj9ka.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1126&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Be Shark Smart sign.</span>
<span class="attribution"><span class="source">Alison Kock</span></span>
</figcaption>
</figure>
<p>Shark safety advice is geared towards reducing the probability of an encounter between people and large, predatory sharks. There is always a chance of encountering a shark in areas where they occur, but some locations, times and situations are more risky than others. </p>
<p>Sharks do not randomly swim around the ocean. They frequently follow specific migration <a href="http://www.nature.com/nature/journal/v465/n7301/full/nature09116.html">routes</a>, predictable feeding opportunities and are temporarily <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0083249">resident</a> in some areas, either to feed, reproduce or rest. </p>
<p>By avoiding times of higher risk one can significantly reduce the likelihood of encountering a shark.</p>
<h2>Hot spots off South Africa’s coast</h2>
<p>The predator-prey relationship between great white sharks and Cape fur seals provides a good case of how effective this can be. At Seal Island, False Bay off the Western Cape coast, over 80% of seals attacked are inexperienced seal pups because they swim in areas and at times of high shark <a href="http://www.capetown.gov.za/en/EnvironmentalResourceManagement/projects/MarineCoastal/Documents/CoastalMngtProg2015/Chapter_17_Shark_Safety.pdf">risk</a>. More experienced adult seals avoid these high risk conditions and are rarely <a href="http://www.iol.co.za/scitech/science/environment/baby-seals-get-wise-to-great-whites-1.1846682">attacked</a>.</p>
<p>In general, seal colonies and adjacent beaches in South Africa, from Cape Point in the Western Cape to another coastal city Port Elizabeth, are great white shark <a href="http://www.ultimate-animals.com/best-places-to-see-great-white-sharks/">hotspots</a>. Encountering a shark in these areas is relatively high. River mouths and adjacent beaches in sub-tropical and tropical areas of southern Africa are frequented by <a href="http://www.oceansafrica.com/bull-shark-zambezi/">bull sharks</a> for feeding and reproduction. </p>
<p>In some cases the higher risk may be seasonal, such as in False Bay, where great whites are seasonally more abundant near beaches over <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0055048">summer time</a>. Sometimes higher risk is associated with major events, such as the annual sardine run along the east and KwaZulu Natal coasts when various shark species follow an abundance of fish along the <a href="http://www.sardinerun.com/sardinerun.asp">coast</a>. Bull sharks are known to be more active following floods and <a href="http://www.abc.net.au/local/stories/2015/05/05/4229778.htm">heavy rains</a>. </p>
<p>At a smaller scale, shallower is better. Even though sharks are capable of swimming in very shallow water, most shark activity is in <a href="http://www.flmnh.ufl.edu/fish/sharks/attacks/howwhen.htm">deeper water</a>. Shark Spotters in False Bay record over 70% of great white shark sightings behind the surf zone, in deeper <a href="http://sharkspotters.org.za/shark-attack-incident-report-muizenberg-1-august-2014">water</a>. </p>
<p>Sometimes predicting or identifying risky situations is not possible and on average South Africa experiences four shark bites, two of them fatal, in a <a href="http://www.sharkattackdata.com/place/south_africa">year</a>. In some years there are no incidents at all; in others there have been up to eight. </p>
<h2>Sharks like to surprise their prey</h2>
<p>Terrestrial predators like lions and leopards use vegetation and topography to ambush their prey. Similarly, large sharks like to hunt near drop-offs, in-between sand banks and on the edge of <a href="http://www.sharkwatchsa.com/en/blog/category/482/post/2020/predator-prey-research-michelle-jewell/">kelp forests</a>, where they wait to surprise seals, fish or turtles swimming <a href="http://animals.howstuffworks.com/fish/sharks/dangerous-place-shark-attack.htm">through</a>. Sharks also use low light like dawn and dusk and murky water to hide in, and sneak up on their prey. Sharks have a sensory advantage in these <a href="http://news.nationalgeographic.com/news/2004/08/0804_040804_shark_attack_2.html">conditions</a>. </p>
<p>Sharks, especially bull sharks, are attracted to areas with high sewerage outfalls or other effluents, such as near <a href="http://news.nationalgeographic.com/news/2004/08/0804_040804_shark_attack_2.html">abattoirs</a>. Fishing harbours, and areas used regularly by fishermen should be avoided, especially when fish catches are high. </p>
<p>There are a number of visual cues one can use to identify such high risk times. Diving seabirds and dolphin sightings indicate the presence of bait fish like sardine, anchovy, and herring. Lots of fishermen are a good cue that the fish are <a href="https://www.capetown.gov.za/EN/ENVIRONMENTALRESOURCEMANAGEMENT/TIPS/Pages/SharkSafetyTips.aspx">biting</a>. The baitfish attracts larger predatory fish and other smaller sharks, which are prey for large sharks. Contrary to popular belief large sharks are not <a href="http://theplanetd.com/a-dolphin-swim-in-shark-country/">deterred</a> by dolphins. In fact dolphins and large sharks will often feed on the same fish and in some cases dolphins are potential <a href="http://www.dailytelegraph.com.au/news/nsw/monster-sharks-brutal-attack-on-dolphin-at-newcastles-burwood-beach/story-fni0cx12-1227186199991">food</a> for large sharks. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/90663/original/image-20150803-5978-1rkg8d3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/90663/original/image-20150803-5978-1rkg8d3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/90663/original/image-20150803-5978-1rkg8d3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/90663/original/image-20150803-5978-1rkg8d3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/90663/original/image-20150803-5978-1rkg8d3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/90663/original/image-20150803-5978-1rkg8d3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/90663/original/image-20150803-5978-1rkg8d3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/90663/original/image-20150803-5978-1rkg8d3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sharks and dolphins feeding together.</span>
<span class="attribution"><span class="source">Morne Hardenberg</span></span>
</figcaption>
</figure>
<h2>Stay in a group, and research your area</h2>
<p>One of the best pieces of advice is to stay in a group. Sharks are more likely to attack a solitary individual, a group offers extra vigilance to spot an approaching shark and there is someone close by to help in an emergency. </p>
<p>Do not enter the water if you are bleeding from an open wound, and enter with caution if you are <a href="http://www.flmnh.ufl.edu/fish/sharks/isaf/mens.htm">menstruating</a>. It is unlikely that this will attract sharks from far, but sharks have an acute sense of smell and it may mean you are singled out if a shark is close by. </p>
<p>Avoid wearing contrasting colours and shiny jewellery because sharks see contrasting colours very well and the shimmer given off by jewellery <a href="http://www.surfscience.com/topics/surfing-lifestyle/life-as-a-surfer/avoiding-shark-attacks/">resembles</a> the shine of fish scales. This is particularly true for bull sharks in murky water. </p>
<p>There are a number of shark deterrents on the market, from magnetic bracelets to wetsuits which mimic sea snakes. Consider using a personal <a href="https://www.sharkshield.com/technology">Shark Shield</a> which is an electronic device used to repel sharks. To date this electric shark repellent is the only deterrent on the market which is backed up by independent <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0062730">research</a>. However, its effect is species and behaviour dependent and does not provide a 100% guarantee. </p>
<p>Where available choose to use beaches with shark safety strategies, like <a href="http://sharkspotters.org.za/">shark spotters</a>, life guards or exclusion nets in place. If visiting a remote beach, make sure that you have a basic medical first aid kit as well as emergency numbers easily accessible. </p>
<p>Bear in mind that each location will be affected <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0068554">differently</a> according to the species present, and its reason for being there, as well as your activity like swimming or surfing. Research your area or contact a local shark scientist for more information. Importantly before heading out into the water again, take a few minutes to ask locals about recent shark sightings and assess the prevailing conditions for any unusual marine activity.</p><img src="https://counter.theconversation.com/content/45169/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alison Kock works for Shark Spotters. She receives funding from the Save Our Seas Foundation, Two Oceans Aquarium and University of Cape Town. She is affiliated with the South African Shark Conservancy, University of Cape Town and South African Institute of Aquatic Biodiversity.</span></em></p>What lies behind shark safety methods.Alison Kock, Research Manager, Shark Spotters and Honorary Research Associate, South African Institute for Aquatic BiodiversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/448722015-07-22T10:36:57Z2015-07-22T10:36:57ZWhite shark populations are growing. Here’s why that’s good news<figure><img src="https://images.theconversation.com/files/89092/original/image-20150720-12564-19uu9v9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Where there are groups of seals, there are sharks.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/masseea/3971990475/in/photostream/">Massachusetts Office of Energy and Environment</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>When bald eagle populations rebounded, people rejoiced. When alligators came back from the brink of extinction, most of us agreed it was a good thing. But tell people how happy you are that the great white shark population is on the rise, and you won’t find many who will join in the celebration.</p>
<p>It’s understandable. We have an inherent and sensible fear of predators that can eat us as we enjoy a summer swim, and the recent attacks by other shark species in the Carolinas have been frightening and traumatic. And many people this week have watched the <a href="https://www.youtube.com/watch?v=xrt27dZ7DOA">video</a> of a professional surfer fend off an attack from a white shark. But in the balance, healthy shark populations are part of a healthy ocean, and we depend on a healthy ocean for our very lives.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/xrt27dZ7DOA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Pro surfer Mick Fanning escapes a shark encounter earlier this week.</span></figcaption>
</figure>
<p>The world’s oceans provide humankind with critical sources of food. They help regulate the Earth’s climate and remove carbon dioxide from the atmosphere. Even those of us who live thousands of miles from the coast are very much in the oceans’ debt for many of the comforts and conveniences of our existence. </p>
<p>Sharks – occupying the top of the marine food chain as they do – are a visible sign of the how our seas are faring. We don’t know what would happen to the oceans without them, but we know this: removing apex predators – or any species – from the web of life can have consequences that are just as problematic for people as the “problem” species was.</p>
<h2>Sharks on rebound</h2>
<p>Like it or not, sharks are part of a balanced ocean ecosystem. After a decline of up to <a href="http://www.nmfs.noaa.gov/pr/species/Status%20Reviews/nwa_dusky_shark_sr_2014.pdf">90% for some species</a> in the United States, they are beginning a <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0098078">gradual rise</a> toward the <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0099240">numbers</a> of a century ago.</p>
<p>That suggests some of the damage we’ve done to the oceans has been reversed, and that’s something to celebrate.</p>
<p>I have no wish to minimize or make light of the trauma suffered by shark-attack victims and their families, which includes <a href="http://www.al.com/news/index.ssf/2015/07/why_are_so_many_shark_attacks.html">eight</a> people in North Carolina this year. Quite the reverse: I hope civic leaders and beachgoers will take these events seriously, because they’re going to happen more often. </p>
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<figcaption><span class="caption">The Atlantic White Shark Conservancy tags sharks off the coast of Cape Cod last summer.</span></figcaption>
</figure>
<p>It won’t be a rapid change. Sharks take eight or more years to reach reproductive age, and their gestation periods can be as long as 18 months, with a year or two between pregnancies, so we won’t be seeing a shark baby boom. </p>
<p>If it seems that they’re turning up in ever greater numbers, it’s because incidents are more visible now: there are more of us and we’re all ready with our smartphones, capturing and sharing footage whenever someone yells “Shark!”</p>
<p>While the white shark population rise won’t be rapid, it will be noticeable. These will be numbers few of us have seen in our lifetimes. </p>
<p>We can trace it back to another success story. With the passage of the Marine Mammal Protection Act in 1972, seal and sea lion populations began to rebuild along the West Coast. White sharks eat seals and sea lions, and having more of their favorite food available enabled them to make a comeback, too. </p>
<p>Now we’re seeing seals returning to parts of the Northeast where they haven’t been for nearly a century. We can expect that white sharks won’t be far behind.</p>
<h2>Learning how to coexist</h2>
<p>As seals and sharks return to their former numbers and territories, we will need to make adjustments.</p>
<p>We have protected these animals from being killed, but now we have to relearn how to live alongside them. Marine mammals will reclaim beaches that we’ve become accustomed to using, and sharks will follow to prey on them. </p>
<p>Because these changes will happen gradually, there’s no need to be caught unaware. We know it’s going to happen; we need to start planning how we’re going to deal with this at a community and personal level.</p>
<p>We can take steps to coexist safely with sharks. Additional beach safety personnel can help spot sharks near swimming areas. Guidelines about swimming a safe distance from seal colonies and fishing areas where sharks may be found could help. </p>
<p>There’s even talk of <a href="http://sawfish.saveourseas.com/projects/counting_sharks_with_drones">deploying drones</a> to keep a lookout for sharks. We also need to be prepared to cede some beaches back to the species that once dominated them.</p>
<figure>
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<figcaption><span class="caption">Beachgoers keep a white shark on Cape Cod alive before it’s captured and put back into the ocean.</span></figcaption>
</figure>
<p>Changes in our behavior will help, but a change in our mindset is also in order. We’re going to have to accept that when we swim in the ocean, we enter a world that is not our own, one where we have no guarantee of safety. We already know there’s a risk of drowning, even for strong swimmers, and we accept this risk when we go into the ocean. The risk of shark attack is – and will remain – much lower.</p>
<p>There is, in fact, some evidence that attitudes are starting to change. Earlier this month, beachgoers in Cape Cod kept a beached white shark alive long enough for volunteers and researchers to release it back into the sea, whereas in previous years it might have been <a href="http://dotearth.blogs.nytimes.com//2015/07/17/from-white-sharks-to-tigers-can-we-get-comfortable-with-carnivores/">deliberately killed</a> or left to die. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/89093/original/image-20150720-12567-pddv95.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/89093/original/image-20150720-12567-pddv95.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/89093/original/image-20150720-12567-pddv95.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=371&fit=crop&dpr=1 600w, https://images.theconversation.com/files/89093/original/image-20150720-12567-pddv95.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=371&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/89093/original/image-20150720-12567-pddv95.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=371&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/89093/original/image-20150720-12567-pddv95.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=466&fit=crop&dpr=1 754w, https://images.theconversation.com/files/89093/original/image-20150720-12567-pddv95.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=466&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/89093/original/image-20150720-12567-pddv95.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=466&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Education and warnings, such as this one in California, can help.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/gzahnd/3265205583/in/photolist-4YEbHJ-dbiHmH-8syaTy-5Yx2RZ-83FPet-oPVyR7-65FpxW-tQJG57">Gino Zahnd/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>A growing white shark population is a success story where few are found. It’s like money in the bank for a sound ecosystem. For decades, most of us didn’t give sharks a second thought, but now we will have to. That’s part of the give-and-take in any relationship. </p>
<p>Think of it as a compromise that keeps the marriage between us and the natural world going. </p>
<p>If we can make some adjustments in our thinking and behavior, we can minimize conflicts between sharks and people. They may be the ones blessed with the teeth, but we’re the ones blessed with the brains.</p><img src="https://counter.theconversation.com/content/44872/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>George Burgess does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A rash of white shark attacks this summer points to a rebounding population in the US – a sign of healthier oceans and the need to coexist with this apex predator.George Burgess, Director, Florida Program for Shark Research and Coordinator of Museum Operations, Florida Museum of Natural History, University of FloridaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/325602014-10-07T03:19:37Z2014-10-07T03:19:37ZResponse to the latest shark bite is fuelled by myth and retribution<figure><img src="https://images.theconversation.com/files/60951/original/pf2qm57s-1412635254.jpg?ixlib=rb-1.1.0&rect=4%2C0%2C3259%2C2218&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Western Australia has killed two great white sharks after a surfer was seriously injured last week.</span> <span class="attribution"><span class="source">Sharkdiver.com/Wikimedia Commons</span></span></figcaption></figure><p>When I used to tell people that I did my PhD on the politics of shark attacks, they would ask, “Is there a politics to shark attacks?” Nobody asks that any more. Now they just say, “Oh, like in Western Australia?”</p>
<p>Those politics have been deployed again in the past week, after surfer Sean Pollard <a href="http://www.abc.net.au/news/2014-10-02/shark-attack-off-esperance/5785820">lost an arm and his other hand</a> in an incident near Esperance on the state’s south coast. </p>
<p>In response, the Barnett government implemented its “imminent threat” <a href="http://www.dpc.wa.gov.au/Consultation/Documents/Appendix%203%20Guidelines%20for%20fishing%20for%20sharks%20posing%20an%20imminent%20threat.pdf">policy</a>, which calls for the setting of baited drumlines in an area where a shark bite incident has occurred. (The policy, which remains in place despite the <a href="https://theconversation.com/western-australian-shark-cull-policy-dumped-experts-react-31621">demise of the wider shark cull</a>, also allows a shark swimming near a popular beach to be pre-emptively killed.) Two protected great white sharks were <a href="http://www.9news.com.au/national/2014/10/02/14/03/man-loses-both-arms-in-wa-shark-attack">killed</a> as a result. </p>
<p>Yet the exact details of the original incident are far from clear. Pollard said he believed <a href="https://au.news.yahoo.com/a/25163473/shark-victim-tells-of-feeding-frenzy">two bronze whalers</a> were responsible. Meanwhile, scientists who examined his surfboard believe that <a href="https://au.news.yahoo.com/a/25186141/wa-expert-says-white-shark-attacked-surfer">one white shark</a> may have been involved, although they were <a href="http://www.fish.wa.gov.au/About-Us/Media-releases/Pages/Examinations-of-white-sharks-complete-.aspx">unable to confirm</a> whether either of the two sharks that were later killed was responsible.</p>
<h2>Myths and rogues</h2>
<p>The myth that sustains this policy goes something like this: individual large sharks pose a threat because they are territorial. A shark that bites someone is likely to do it again, and even if there is not an incident now, it is better to kill the shark because it may return. </p>
<p>We have heard this logic before … in the movie Jaws. The policy is predicated on a fictional Hollywood myth that “<a href="http://www.perthnow.com.au/news/western-australia/premier-colin-barnett-targets-rogue-sharks-threatening-wa-beachgoers-after-drum-line-policy-is-scrapped/story-fnhocxo3-1227056468863">rogue</a>” sharks will return to an area and pose a threat to beachgoers and surfers. </p>
<p>The story of serial-killing sharks, however, is not the most concerning aspect. The real problem is how this myth serves as a distraction from a bigger issue. </p>
<p>There continue to be serious and fatal shark bites along the Australian coast that are horrific and life-changing for those involved, their loved ones and their communities. It is time for serious efforts to try and reduce the risk of shark bites based on science and common sense beach safety. But the WA government’s imminent threat policy is not a serious effort at shark bite prevention. </p>
<h2>Safety… or revenge?</h2>
<p>WA’s Jaws-style policy is designed to provide public catharsis through retribution, not public safety. The imminent threat policy can be enacted to kill sharks regardless of whether there are any people in the water, or whether the shark was involved in an incident, or whether killing it improves beach safety, or whether the species is protected by law. In short, this is closer to an old-fashioned witch hunt than to sound public policy. </p>
<p>But it gets worse. While we should give WA credit for spending millions of dollars on scientific tags and testing new non-lethal measures, the latest episode led the Department of Fisheries to kill a white shark that had an internal acoustic tag. So the fiction-based policy that doesn’t help beach safety just undermined a scientific program that does. </p>
<p>Meanwhile, the policy also provides a false sense of security by painting a picture of one shark as the issue – the “problem shark”. </p>
<p>How do we improve this situation, both politically and socially? Here are a few ideas:</p>
<p><strong>This is about the people, not the sharks.</strong> </p>
<p>It is important to hit the pause button and remember that this issue has touched communities all over Australia. This year has seen fatal shark bites on Australia’s east coast, involving <a href="http://www.smh.com.au/nsw/christine-armstrong-63-dies-on-regular-morning-swim-after-shark-strikes-20140403-361jp.html">Christine Armstrong in Tathra</a> and <a href="http://www.bbc.com/news/uk-wales-north-east-wales-29132909">Paul Wilcox in Byron Bay</a>, as well as in the west. After the intensity of these events fades, the difficulty and tragedy will remain and community support for the victims and their families is essential.</p>
<p><strong>This is about the government, not the sharks.</strong> </p>
<p>When it comes to beach safety, governments across Australia need to redirect their focus onto public education and science. The facts are simple. We cannot shark-proof Australia, so public education is the only real way forward. This is a way for WA and the other states to lead and bring people together, rather than setting groups apart with divisive policies. Everyone is in favour of better awareness and education but this remains the missing piece. </p>
<p><strong>This policy could get worse, not better.</strong> </p>
<p>At the moment, the Barnett government appears to support the killing of uninvolved, protected, scientifically tagged great white sharks. One tagged shark has already been killed, and it is possible that things could get even worse from here. With the start of the summer beach season, I expect there will be pressure to begin killing tagged great whites that set off acoustic alarms near beaches. The government has noted that this will not happen, but it is a logical next step in the current thinking. </p>
<p>In all, I hope for a safe, quiet summer with no human-shark encounters. I also hope that science can be used as the basis for public policy. Movie myths make for bad policy and the public deserves better. </p>
<p>The question now is whether the latest tragedy can serve as a tipping point for real shark bite prevention.</p><img src="https://counter.theconversation.com/content/32560/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christopher Pepin-Neff does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>When I used to tell people that I did my PhD on the politics of shark attacks, they would ask, “Is there a politics to shark attacks?” Nobody asks that any more. Now they just say, “Oh, like in Western…Christopher Pepin-Neff, Lecturer in Public Policy, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/283652014-07-01T13:54:55Z2014-07-01T13:54:55ZHow humans can really avoid shark attacks and help protect vulnerable species<p>The plan to use baited traps to catch and kill sharks off the coast of Western Australia caused considerable controversy when it was announced last year, with critics calling the shark cull ineffective, inhumane, and irresponsible. </p>
<p>Now the Western Australian state government has published a <a href="http://www.dpc.wa.gov.au/Consultation/Documents/PER_Western%20Australia%20Shark%20Hazard%20Mitigation%20Drum%20Line%20Program.pdf">review</a> of the trial cull between January and April of this year, and has recommended that it continue until 2017. While the review seeks to address concerns and to allay any misconceptions, it fundamentally supports the continual culling of sharks with no scientific justification. The report states:</p>
<blockquote>
<p>there is conjecture about the reasons for recent increases in shark attacks in Western Australian water [and] there is currently insufficient evidence to clearly establish a cause.</p>
</blockquote>
<p>Where then without scientific evidence is the justification to continue culling several shark species, including bull, tiger and great white sharks?</p>
<p>The increased spate of shark attacks in the past ten years is cause for concern for the tourism industry. The report argues that the programme aims to enhance public safety by capturing potentially dangerous sharks that come close to popular beaches and surfing spots during summer. </p>
<p>The cull still fails to address the matter of shark species, in particular the great white, which is <a href="http://www.iucnredlist.org/details/3855/0">listed as vulnerable</a> by the International Union for Conservation of Nature. </p>
<p>The justification for continuing the culling using drum lines – baited hooks attached to floating, anchored barrels – is questionable. The report provides information on a “comprehensive risk assessment” which concluded that the programme posed “negligible risk to the target species, non-target species of marine fauna and the broader ecosystem.” </p>
<p>Sharks are essential apex predators, ultimately helping to regulate and maintain the balance of marine ecosystems. While they have been mislabelled as ferocious killers, of the <a href="http://www.bbc.co.uk/news/world-asia-27304580">172 sharks caught</a> none were great whites. This seems to be an expensive and unscientific failure, as the report discloses that in the 20 attacks in Western Australia of the past 100 years, great whites have been responsible for 11</p>
<p>It was also thought that the government was aware that numbers of great whites at the time of the project were lower than at other times of the year. The report quotes evidence showing that bull sharks and tiger sharks are responsible for most shark attacks around the world and that the number of unprovoked attacks is rising.</p>
<p>Where is the evidence directly related to the Western Australian coasts to back up these statements? </p>
<p>Alarmingly, the report shows consultation meetings were held without including environment groups, due to their position being “already known”. One wonders how there could ever have been a fair and balanced debate if some viewpoints were ignored.</p>
<p>The report recommends that trapping and culling recommence in mid-November each year over the period of 2014-2017, in an attempt to capturing large great whites – even though it states that “perhaps the most prevalent criticism of the programme is that it is not based on science”. Indeed, most of the scientific references used to support the report’s conclusions regarding catching sharks with drum lines and impact on by-catch are too outdated to support any conclusions. More quality research data is required for this, yet the trial has produced little if any.</p>
<p>The drum lines have also resulted in casualties beyond just sharks, ensnaring seven rays and one <a href="http://www.fishesofaustralia.net.au/home/species/868">northwest blowfish</a>, but fortunately no turtles, dolphins or whales.</p>
<p>The inadequacies in many areas of the report display an inability to recognise the threat we are creating for these vulnerable species at the expense of humans having a “good, shark free holiday” on the beaches of Western Australia. There was a positive note in the review that provides a comprehensive suite of shark hazard mitigation strategies for the future. These include commitments for more research into shark behaviour, shark deterrents and detection, acoustic tagging, aerial patrols, equipment for <a href="http://surflifesavingwa.com.au/">Surf Life Saving WA</a>, a beach enclosure, beach watchtowers and community awareness initiatives. </p>
<p>Shark hazard mitigation is a complex issue. No clear cause has been established for the increase in attacks – seven deaths in three years between 2010 and 2013. The simplest would be to leave the sharks alone. Humans, if they don’t want to take the risk, shouldn’t go in the water.</p><img src="https://counter.theconversation.com/content/28365/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicholas Ray does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The plan to use baited traps to catch and kill sharks off the coast of Western Australia caused considerable controversy when it was announced last year, with critics calling the shark cull ineffective…Nicholas Ray, Senior Lecturer, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.