tag:theconversation.com,2011:/id/topics/porpoises-13724/articlesPorpoises – The Conversation2023-01-19T06:11:41Ztag:theconversation.com,2011:article/1980902023-01-19T06:11:41Z2023-01-19T06:11:41ZOffshore wind farm construction is noisy – but gadgets used to protect marine mammals are working<figure><img src="https://images.theconversation.com/files/505122/original/file-20230118-22-euadqv.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4595%2C3061&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Harbour porpoises are the most common toothed whale in the turbine-rich North Sea.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/harbour-porpoise-phocoena-2137783321">Onutancu/Shutterstock</a></span></figcaption></figure><p><a href="https://energy.ec.europa.eu/topics/renewable-energy/offshore-renewable-energy_en#:%7E:text=The%20deployment%20of%20offshore%20wind,the%205%20EU%20sea%20basins.">The European Union</a> had 14.6 gigawatts (GW) of offshore wind energy installed in 2021, and this is projected to increase by at least 25 times in the next ten years. While an expanding renewable energy sector is necessary to replace fossil fuels and slow climate change, it must not come at a cost to <a href="https://theconversation.com/uk/topics/biodiversity-486">Earth’s embattled wildlife</a>. </p>
<p>To date, most offshore wind turbines have been built using fixed foundations, typically steel piles that are driven into the seabed with hydraulic hammers – often very large ones. The noise that pile-driving generates can be heard tens of kilometres from the source as short and sharp concussions like gunfire.</p>
<p>Sound travels much more efficiently in water than in air. Marine mammals like whales and porpoises use it to communicate over long distances, sense the environment and locate prey. This dependence on sound makes marine mammals <a href="https://doi.org/10.1644/07-MAMM-S-307R.1">particularly vulnerable</a> to the effects of man-made noise, including the noisy construction of offshore wind farms. Pile-driving can deafen, injure or even kill marine mammals at close range.</p>
<p>The harbour porpoise is the smallest and <a href="https://www.frontiersin.org/articles/10.3389/fmars.2020.606609">most common</a> species of cetacean in the North Sea, where EU countries hope to generate <a href="https://windeurope.org/policy/joint-statements/the-esbjerg-offshore-wind-declaration/">150 GW</a> of offshore wind energy by 2050. Like bats, these relatives of whales and dolphins emit clicks to echolocate almost continuously. This helps them find and identify objects, including food. Acoustic deterrents, small devices which emit pulses of sound, are used to scare marine mammals away from where wind farms are being built to protect them from the noise generated by pile-driving. Until recently though, no one was sure how well these deterrents worked.</p>
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<img alt="The dorsal fins and backs of two harbour porpoises emerging from the water." src="https://images.theconversation.com/files/505126/original/file-20230118-14-1r7n63.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/505126/original/file-20230118-14-1r7n63.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/505126/original/file-20230118-14-1r7n63.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/505126/original/file-20230118-14-1r7n63.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/505126/original/file-20230118-14-1r7n63.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/505126/original/file-20230118-14-1r7n63.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/505126/original/file-20230118-14-1r7n63.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">
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<span class="caption">Harbour porpoises, as the name suggests, are found in coastal waters.</span>
<span class="attribution"><span class="source">University of Aberdeen</span>, <span class="license">Author provided</span></span>
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<p>My colleagues at the University of Aberdeen’s Lighthouse Field Station and the University of St. Andrews’ Sea Mammal Research Unit developed <a href="https://doi.org/10.1098/rsbl.2022.0101">a portable acoustic recorder</a> which can detect the movements of harbour porpoises. Using an array of these recorders during pile-driving at an offshore wind farm in north-east Scotland, we showed that acoustic deterrents work – porpoises swim directly away from the pulses of sound, ameliorating the most severe impacts of construction at sea. </p>
<h2>Fighting noise with noise</h2>
<p>A range of <a href="https://doi.org/10.3390/jmse9080819">measures</a> have been deployed to minimise the harm from offshore wind farm construction. Acoustic deterrent devices, which are switched on before pile-driving begins, are supposed to empty the sea of marine mammals tens to hundreds of metres around the construction site, where the noise is expected to be most damaging. These <a href="https://doi.org/10.3354/meps10482">electronic devices</a> were originally developed for use in the aquaculture industry to deter seals from fish farms.</p>
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<img alt="A wind turbine on a yellow platform in the ocean." src="https://images.theconversation.com/files/505128/original/file-20230118-22-rpeyaq.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/505128/original/file-20230118-22-rpeyaq.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/505128/original/file-20230118-22-rpeyaq.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/505128/original/file-20230118-22-rpeyaq.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/505128/original/file-20230118-22-rpeyaq.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/505128/original/file-20230118-22-rpeyaq.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/505128/original/file-20230118-22-rpeyaq.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Offshore wind turbine foundations are driven into the seabed.</span>
<span class="attribution"><span class="source">University of Aberdeen</span>, <span class="license">Author provided</span></span>
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</figure>
<p>Despite <a href="https://doi.org/10.3354/MEPS10100">experimental trials</a>, there is limited evidence to show how well acoustic deterrents work during construction. This is, at least in part, due to the difficulties of working in the marine environment, but also because of the challenges involved in studying animals that are highly mobile, relatively rare and live most of their lives underwater and out of sight. These factors make it very hard to observe how marine mammals react to particular noises or disturbances. Fortunately, we were able to turn the dependence of harbour porpoises on sound to our advantage.</p>
<p>Recent advances in <a href="http://dx.doi.org/10.1371/journal.pone.0229058">passive acoustic monitoring</a> meant that we could use a sound recorder connected to a small cluster of underwater microphones, called hydrophones, to study porpoise movements. By measuring tiny differences in the time of arrival of porpoise echolocation clicks at the four hydrophones, we identified the direction from which they were echolocating. The harbour porpoise’s echolocation beam is <a href="https://doi.org/10.1121/10.0001376">narrow and forward-facing</a>, and so from these findings, we were able to determine the direction in which they were swimming.</p>
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<img alt="A drum covered in electronic devices is lowered over the side of a boat into the ocean." src="https://images.theconversation.com/files/505120/original/file-20230118-20-8vvg3x.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/505120/original/file-20230118-20-8vvg3x.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/505120/original/file-20230118-20-8vvg3x.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/505120/original/file-20230118-20-8vvg3x.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/505120/original/file-20230118-20-8vvg3x.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/505120/original/file-20230118-20-8vvg3x.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/505120/original/file-20230118-20-8vvg3x.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">
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<span class="caption">A hydrophone cluster being deployed.</span>
<span class="attribution"><span class="source">University of Aberdeen</span>, <span class="license">Author provided</span></span>
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<p>We found that when acoustic deterrents were in use, the clicks of harbour porpoises we detected indicated they were swimming directly away from the construction site. This proves that acoustic deterrent devices can make offshore wind farm construction safer. </p>
<p>We did detect responses among harbour porpoises up to 7 km from the construction site, suggesting that these deterrent devices may be almost too good at their job. Such a long-distance effect could displace animals from important feeding sites and highlights the importance of a balance between preventing injuries and minimising disturbance.</p>
<p>Our portable acoustic recorder can now improve protection for marine mammals by more accurately determining how they respond to disturbance across a wide range of habitats. It will also allow researchers to gauge the effectiveness of measures used to minimise disturbance during wind farm construction or other activities, including animal deterrents and systems for reducing the noise produced by piling at construction sites.</p>
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<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p class="fine-print"><em><span>Isla Graham received funding from Moray Offshore Wind Farm (East) Ltd. The funding body had no input in data collection, data analysis or interpretation. The aims, scope and experimental design of the study were developed by the authors to meet Moray Offshore Wind Farm (East) Ltd planning consent conditions. These were agreed by the regulator Marine Scotland Licensing and Operations Team following consultation with statutory advisors represented on the Moray Firth Regional Advisory Group (MFRAG), a stakeholder group that was established by the Scottish government to oversee the monitoring programme.</span></em></p>A new acoustic recorder could track the movements of marine mammals more accurately.Isla Graham, Research Fellow, School of Biological Sciences, University of AberdeenLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/782392017-06-01T10:09:40Z2017-06-01T10:09:40ZThe campaign to save Mexico’s vaquita porpoise faces the same problems as the War on Drugs<figure><img src="https://images.theconversation.com/files/171784/original/file-20170601-25664-ksh24y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="http://www.fisheries.noaa.gov/pr/species/mammals/porpoises/vaquita.html">Paula Olson/NOAA</a></span></figcaption></figure><p>Actor Leonardo DiCaprio recently took to social media to <a href="http://www.ibtimes.co.uk/endangered-vaquita-leonardo-dicaprio-urges-mexican-president-save-sea-pandas-1621838">demand action</a> to protect the endangered vaquita porpoise, a species native to the Gulf of California in Mexico that is on the verge of extinction. A week later, the World Wildlife Foundation (WWF) <a href="http://www.independent.co.uk/environment/vaquita-extinct-world-rarest-animal-mexico-totoaba-swim-bladder-save-conservation-wwf-warns-a7738351.html">joined the fray</a> by releasing a document with <a href="https://s3-us-west-2.amazonaws.com/makeyourmark.panda.org/vaquita_report/VAQUITA+LR+SINGLES.pdf">ten policy suggestions</a> that the Mexican government should implement to protect the mammal.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"862485495632285696"}"></div></p>
<p>The Mexican government has spent ten years and <a href="http://www.animalpolitico.com/2017/04/vaquita-marina-inversion-proteccion/">more than US$60m</a> trying to clamp down on the illegal killing of vaquita, with no success. The message from critics is “double your efforts”. </p>
<p>Yet little is being done to reduce the reason the porpoises are killed in the first place. Vaquita are commonly caught up in the gillnets used to catch the Mexican totoaba fish, which is is highly prized as a culinary delicacy in <a href="https://www.theguardian.com/environment/2017/may/16/chinese-appetite-totoaba-fish-bladder-threatens-rare-vaquita">countries such as China</a>. Focusing attention and condemnation on the supply side of this illegal trade without addressing the demand is reminiscent of the <a href="https://theconversation.com/a-decade-of-murder-and-grief-mexicos-drug-war-turns-ten-70036">War on Drugs</a> that Mexico has also been fighting for a decade – and has about as much chance of succeeding in.</p>
<p>Mexico has implemented several programmes to prevent the illegal killing of the vaquita – with tragic results. <a href="https://www.gob.mx/vaquita-marina">These have included</a> a two-year <a href="http://www.greenpeace.org.uk/oceans/problems/gill-netting">ban on gillnets</a> and the creation of a natural park in the Gulf of California. Despite these efforts, the population of the vaquita has diminished by more than 90% in the last six years and <a href="http://vaquitafilm.com/wp-content/uploads/2017/02/CIRVA-8-Report-Final.pdf">only around 30 specimens</a> are left. </p>
<p>Following the recommendations of the WWF and others would mean more money and policies to fight the fisheries and illegal supply of vaquita. But the demand driving the killing is coming from countries <a href="https://elephantleague.org/operation-fake-gold/">such as China</a>, where there is minimal regulation and a growing elite willing to pay as much as for US$20,000 for exotic seafood dishes.</p>
<p>This situation is all too similar to the so-called War on Drugs. Since 2006, the Mexican Government has fought drug production, trafficking and organised crime mainly through a <a href="http://ppd.cide.edu/documents/302668/0/Drug%20Policy%20in%20Mexico">law and order</a> enforcement approach. This has involved mobilising military forces inside the country, as well as intelligence, weaponry and monetary cooperation with the US via the <a href="https://www.state.gov/j/inl/merida/">Mérida Initiative</a>.</p>
<p>However, drug-related violence <a href="http://www.semaforo.mx/">is rising yet again</a> in Mexico. The costs are overwhelming both in social and economic terms. <a href="http://economicsandpeace.org/wp-content/uploads/2016/04/%C3%8Dndice-de-Paz-M%C3%A9xico-2016_ES.pdf">Over the last four years</a>, crime related deaths have reached 44,000 and the violence costs the Mexican economy approximately 13% of its GDP.</p>
<p>Despite the appalling outcome, the Mexican government cannot be accused of not investing and fighting. Over the last ten years, the country’s defence and security budget has <a href="http://ppd.cide.edu/documents/302668/0/Libro%203.pdf">more than doubled</a>, with annual spend totalling more than US$7 billion. Exact figures for the War on Drugs are difficult to calculate but over the period 2006-2012 expenses on drug policies amounted to US$48 billion, with <a href="http://ppd.cide.edu/documents/302668/0/Drug%20Policy%20in%20Mexico">97% of that </a> assigned to law and order related efforts.</p>
<p>And yet the US government is insisting on more. Recently, the US Ambassador to Mexico said that the government should <a href="http://www.elfinanciero.com.mx/nacional/roberta-jacobson-llama-a-redoblar-esfuerzos-contra-narcotrafico.html">redouble its efforts</a> – much like the WWF’s recommendations on the vaquita. Nevertheless, there is no indication that the US government is willing to continue bearing the same law enforcement approach, as their policy efforts are shifting towards <a href="https://www.washingtonpost.com/news/wonk/wp/2016/02/10/the-radical-way-the-presidents-spending-plan-would-change-the-drug-war/?utm_term=.4890c6c280d0">public health</a>, <a href="https://www.washingtonpost.com/news/wonk/wp/2017/04/17/on-drug-policy-one-trump-administration-official-stands-apart/?utm_term=.6218d3804220">demand reduction</a>, and regulating the consumption and production of <a href="https://www.theguardian.com/us-news/2016/nov/08/state-ballot-initiative-election-results-live-marijuana-death-penalty-healthcare">soft drugs like marijuana</a>, which is now legal in several states.</p>
<h2>Global challenge</h2>
<p>South of the border, the number of dead is rising, violence is increasing and production is not diminishing. While in the north, many consumers are enjoying a joint or a line “peacefully”. The percentage of Americans using illegal drugs is increasing, reaching <a href="https://www.drugabuse.gov/publications/drugfacts/nationwide-trends">9.4% – 24.6m people – in 2013</a>. In particular, marijuana and amphetamine consumption has been increasing, which is significant because 40-80% of all marijuana consumed in the US <a href="http://www.rand.org/pubs/research_briefs/RB9559.html">comes from Mexico</a>. And while cocaine use has been slightly decreasing, the US market remains <a href="https://www.unodc.org/documents/wdr/WDR_2010/1.3_The_globa_cocaine_market.pdf">worth around US$35 billion</a> and is one of the main sources of revenue for Mexican drug cartels.</p>
<p>Just like climate change and wildlife conservation, drugs and violence are a global challenge, where responsibilities must be shared and where the demand that drives consumption is the key to illegal trade. Globalisation has created interdependence between countries at many levels. But an enormous sea separates China from Mexico and therefore Chinese consumers have the luxury of ignoring the consequences of their actions.</p>
<p>US consumers would not have that luxury since they share a border with Mexico and their actions would have social and humanitarian consequences. As an example, only <a href="http://www.cicad.oas.org/Main/Template.asp?File=/drogas/elinforme/default_eng.asp">1% of the revenues</a> related to cocaine reach farmers in developing countries, but illegal trade and increasing demand generates violence that affects local economies. While Mexico has the 15th largest economy in the world, the ingredients for a disaster are looming: rising poverty, corruption and violence. If this leads to social and economic breakdown, Mexicans will knock on the US’s door. </p>
<p>It can’t be denied that the Mexican government has a systemic problem when it comes to enforcing the <a href="https://www.wilsoncenter.org/sites/default/files/rios_rule_law_mexico_growth.pdf">rule of law</a>. But it also needs to reevaluate the international recommendations and policies that it applies with broad consequences. </p>
<p>Shortly after Leonardo DiCaprio made his plea, President Peña quickly responded with a commitment that Mexico was <a href="http://www.reuters.com/article/mexico-vaquita-idUSL1N1IE073">already working hard</a>. Unfortunately, it is not a simple matter of resources. If Mexico keeps following the same road, the same outcome will emerge: Mexico puts in the effort, gets the international blame and ultimately carries the corpses.</p>
<p><em>This article was amended to clarify that the vaquita porpoise is killed as a bycatch of the totoaba fish.</em></p><img src="https://counter.theconversation.com/content/78239/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>J. Alejandro Espinosa Herrera receives funding from the Minister of Science of the Mexican Government to pursue his Ph.D. </span></em></p>Both focus too much on controlling supply and not enough on demand.Alejandro Espinosa Herrera, DPhil Candidate in Politics, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/533372016-01-19T12:50:50Z2016-01-19T12:50:50ZTen years after the Thames whale, how are Britain’s sea mammals faring?<p>The British Isles are blessed with a wide variety of sea mammals, with records showing 29 species of whales, porpoises and dolphins and seven species of seals in its waters. But only some of these are regular inhabitants, and when the more unusual species make an appearance it can cause considerable public interest – as happened ten years ago when a northern bottlenose whale, normally found in the deep Atlantic, instead <a href="http://news.bbc.co.uk/1/hi/england/london/4631396.stm">swam up the River Thames</a> in front of the Houses of Parliament and tens of thousands of fascinated onlookers.</p>
<p>While few in the city can have been unaware of what was unfolding in the river, attempts to rescue the whale failed, and <a href="http://news.bbc.co.uk/1/hi/england/london/4635874.stm">it died two days later</a>. The whale, far from its normal habitat, had probably entered the North Sea in pursuit of squid, its principal prey, before becoming lost and, hungry and disoriented, ended up in the Thames Estuary. A <a href="http://www.thameswhale.info/">post-mortem by pathologists</a> from the Zoological Society of London found the cause of death to be a combination of dehydration, physiological stress, cardiovascular collapse and multiple organ failure induced by the stress of repeated strandings and the attempted rescue. </p>
<p>In truth, the tale of the Thames whale says more about human behaviour than whales themselves. But a decade on, it’s interesting to reflect on what we know about the changing fortunes of the remarkable creatures that live in Britain’s waters.</p>
<h2>Cetaceans – whales, dolphins and porpoise</h2>
<p>Of the 29 cetacean species recorded around Britain, 15 are regular inhabitants. But we know very little about all but the most common species. Some species such as fin and <a href="http://www.seawatchfoundation.org.uk/humpback-hooray/">humpback whales</a>, among the principal targets of the early 20th century whaling industry, show signs of recovery, with a marked increase in sightings. </p>
<p><a href="http://seawatchfoundation.org.uk/wp-content/uploads/2012/07/Minke_Whale.pdf">Minke whales</a>, which are still taken in Norwegian waters but in smaller numbers, also show signs of population growth since the 1980s. This may be related partly to ecosystem changes during the 1960s-70s when fish stocks of herring and mackerel collapsed, seemingly taking the pressure off prey fish such as sandeel and sprat for which the whales competed. However, since the mid-1990s, the abundance of minke whales as assessed by large-scale surveys (<a href="http://gcmd.gsfc.nasa.gov/KeywordSearch/Metadata.do?Portal=GCMD&MetadataType=0&MetadataView=Full&KeywordPath=&EntryId=seamap103">SCANS in July 1994</a> and <a href="http://biology.st-andrews.ac.uk/scans2/">SCANS II in July 2005</a>) has shown no significant change.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/108579/original/image-20160119-29783-1s4hf3c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108579/original/image-20160119-29783-1s4hf3c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=360&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108579/original/image-20160119-29783-1s4hf3c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=360&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108579/original/image-20160119-29783-1s4hf3c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=360&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108579/original/image-20160119-29783-1s4hf3c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=452&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108579/original/image-20160119-29783-1s4hf3c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=452&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108579/original/image-20160119-29783-1s4hf3c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=452&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A minke whale lunging through a shoal of sprat in the Inner Hebrides.</span>
<span class="attribution"><span class="source">P Anderwald</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The same applies to <a href="http://seawatchfoundation.org.uk/wp-content/uploads/2012/07/White-beaked_Dolphin.pdf">white-beaked dolphin</a> and <a href="http://seawatchfoundation.org.uk/wp-content/uploads/2012/07/Harbour_Porpoise.pdf">harbour porpoise</a> – although the porpoise is now found more abundantly in the southern North Sea and English Channel, with a corresponding decrease in the northwestern North Sea. This change in distribution may well be related to the abundance of certain prey – sandeel is an obvious candidate since stocks in the northwestern North Sea have declined over the last 20 years.</p>
<p>During the 1990s, deaths of porpoises from accidental capture in fishing gear such as gill nets were thought to be unsustainable, which led to the introduction in 2004 of an <a href="http://jncc.defra.gov.uk/page-5214">EU Regulation (812/2004) aimed at reducing bycatch</a>. At the same time, fishing in the North and Celtic Seas where porpoise bycatch was greatest also declined. However, porpoise deaths from fishing vessels continue, with insufficient monitoring for us to be truly confident of the scale. </p>
<p>Another problem facing marine mammals is that of pollutants: contaminant levels in top predators, which bioaccumulate through the food chain, have declined substantially from when PCBs (polychlorinated biphenyls) and pesticides (DDT and dieldrin) were widespread during the mid-20th century. But they persist in the oceans, with <a href="http://www.nature.com/articles/srep18573">PCB levels in particular around the UK linked with disease</a> among harbour porpoises. Other top predators like bottlenose dolphin and <a href="http://seawatchfoundation.org.uk/wp-content/uploads/2012/07/Killer_Whale.pdf">orca</a> (killer whale) may also be especially vulnerable. That said, there is no clear evidence of significant overall population declines. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/108480/original/image-20160118-31821-1ns8ray.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108480/original/image-20160118-31821-1ns8ray.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=369&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108480/original/image-20160118-31821-1ns8ray.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=369&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108480/original/image-20160118-31821-1ns8ray.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=369&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108480/original/image-20160118-31821-1ns8ray.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=463&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108480/original/image-20160118-31821-1ns8ray.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=463&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108480/original/image-20160118-31821-1ns8ray.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=463&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Harbour seals have been declining in several areas in Britain.</span>
<span class="attribution"><span class="source">Peter Evans</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Pinnipeds – seals</h2>
<p>We know much more about seal populations than whales, thanks mainly to the monitoring efforts of the <a href="http://www.smru.st-andrews.ac.uk/">Sea Mammal Research Unit</a> at the University of St Andrews. With an estimated population size of around 112,000, the UK accounts for 38% of the world’s Atlantic grey seals, which appear to be thriving. The majority (88%) breed in Scotland where, since the 1990s, they have been growing in numbers, particularly around Orkney and parts of the North Sea. Only in the Hebrides have pup birth rates remained fairly static.</p>
<p>By contrast, harbour seals have not fared so well over the same period. At 36,500, Britain’s harbour seals represent around 30% of the European population. Harbour seal counts (made during the autumn moult) were stable or rising until around 2000 when they began to decline in Shetland (down by 30%), Orkney (down 78%) and the Firth of Tay (down 93%). Other regions have been more stable, with those further south recovering from the devastating effect of the <a href="http://www.ncbi.nlm.nih.gov/pubmed/16532603">PDV morbillivirus epidemic in 1988</a> which wiped out more than half their population. We don’t really know what’s behind these changes, but competition for food and the impact of toxins from harmful algae are possible causes. </p>
<p>The effects of climate change on sea mammals is also an issue, due to the effects it has on prey species. The last ten years have seen greater numbers of warm water species such as <a href="http://seawatchfoundation.org.uk/wp-content/uploads/2012/07/Striped_Dolphin.pdf">striped dolphin</a> and <a href="http://uk.whales.org/species-guide/cuviers-beaked-whale">Cuvier’s beaked whale</a>, and a new species, <a href="http://uk.whales.org/species-guide/dwarf-sperm-whale">dwarf sperm whale</a>, added to those species appearing in British waters. Also, in what might seem like a contradictory trend, a bowhead whale, normally closely associated with the Arctic, made its <a href="http://www.bbc.co.uk/news/uk-england-cornwall-31659103">first UK appearance</a> off the Isles of Scilly in February 2015. It’s likely that the next ten years will bring more changes to the status and distribution of different species as they experience changing environmental pressures.</p><img src="https://counter.theconversation.com/content/53337/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>I am Director of a non profit research organisation called Sea Watch Foundation. That organisation receives contracts from government conservation bodies such as JNCC and Natural Resources Wales, to undertake research projects. I am also a member of a consortium of academic institutions funded by NERC participating in a Marine Ecosystems Research Programme. I am a member of a scientific Advisory Panel for the Joint Industry Program on Sound and Marine Life. I have no political affiliation. </span></em></p>It didn’t turn out well for the whale who went to Westminster, but others have made a happy home in British waters.Peter Evans, Honorary Senior Lecturer, Bangor UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/346902014-11-26T00:05:34Z2014-11-26T00:05:34ZGrey seals in the dock over porpoise murder mystery<figure><img src="https://images.theconversation.com/files/65505/original/image-20141125-4231-14vrgr8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">But I didn't do it on porpoise, your honour.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/10565417@N03/6246553136">jidanchaomian</a></span></figcaption></figure><p>It’s one of the big mysteries in my career as a marine biologist. Something lurking in the seas off Britain has been chomping away at local porpoises and none of the usual suspects fit the bill. Now scientists have finally identified the cuddly culprit.</p>
<p>I first became aware of the attacks on porpoises – beakless, smaller relatives of dolphins – as I run the <a href="http://www.ukshark.co.uk">UK shark tagging programme</a> and am often asked to comment on possible sightings. In both 2010 and 2011 I was sent pictures from the Norfolk coast of porpoise carcasses with a considerable amount of tissue bitten away. </p>
<p>The common assumption was that these were due to shark attacks. However none of the photographs of the wounds showed the characteristic punctures caused by the multiple rows of shark teeth, such as displayed by human victims of shark attacks. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/65508/original/image-20141125-4253-4seswc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/65508/original/image-20141125-4253-4seswc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/65508/original/image-20141125-4253-4seswc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=219&fit=crop&dpr=1 600w, https://images.theconversation.com/files/65508/original/image-20141125-4253-4seswc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=219&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/65508/original/image-20141125-4253-4seswc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=219&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/65508/original/image-20141125-4253-4seswc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=276&fit=crop&dpr=1 754w, https://images.theconversation.com/files/65508/original/image-20141125-4253-4seswc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=276&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/65508/original/image-20141125-4253-4seswc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=276&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 Norfolk porpoise.</span>
<span class="attribution"><span class="source">Tom Buy</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The UK isn’t exactly known for its deadly sea beasts. While a number of shark species do live round the coast and in the North Sea, the most common are too small to inflict the bites we were dealing with. Larger sharks capable of removing that amount of tissue are very rare. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/65494/original/image-20141125-4217-12494ml.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/65494/original/image-20141125-4217-12494ml.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/65494/original/image-20141125-4217-12494ml.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=595&fit=crop&dpr=1 600w, https://images.theconversation.com/files/65494/original/image-20141125-4217-12494ml.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=595&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/65494/original/image-20141125-4217-12494ml.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=595&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/65494/original/image-20141125-4217-12494ml.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=748&fit=crop&dpr=1 754w, https://images.theconversation.com/files/65494/original/image-20141125-4217-12494ml.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=748&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/65494/original/image-20141125-4217-12494ml.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=748&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Typically reserved coverage in The Sun.</span>
<span class="attribution"><a class="source" href="http://www.thesun.co.uk/sol/homepage/news/3492298/Large-sharks-suspected-as-mutilated-porpoise-washes-up-on-Norfolk-coast.html">The Sun</a></span>
</figcaption>
</figure>
<p>Invariably the popular press claims attacks like these are evidence of great white sharks. After the 2011 find near Great Yarmouth, Norfolk, the <a href="http://www.dailymail.co.uk/news/article-1373982/Shark-alert-Norfolk-coast-savaged-porpoises-wash-beach.html">Daily Mail</a> thought a “giant shark or killer whale could be stalking the coast”, The Sun even said it might be <a href="http://www.thesun.co.uk/sol/homepage/news/3492298/Large-sharks-suspected-as-mutilated-porpoise-washes-up-on-Norfolk-coast.html">Jaws</a> himself.</p>
<p>Given that there are no fully substantiated reports of white sharks in UK waters and that in any case such a shark could quickly dispose of a whole porpoise, <a href="https://theconversation.com/its-silly-season-but-there-is-a-real-shark-threat-to-fear-16975">this is fanciful</a>. </p>
<p>But at last, we have a more likely explanation.</p>
<h2>Whodunnit?</h2>
<p>The unfortunate Norfolk porpoises aren’t alone. In fact, huge numbers of harbour porpoises have been washing up on the shores of the North Sea. They shared the same nasty-looking bite marks.</p>
<p>A team of Dutch scientists has now identified grey seals as the culprits. Their work, reported in the <a href="http://rspb.royalsocietypublishing.org/lookup/doi/10.1098/rspb.2014.2429">Royal Society journal</a>, reveals DNA from grey seals has been found in bite marks on porpoise carcasses.</p>
<p>The researchers examined 721 dead porpoises in detail. The sheer numbers enabled them to identify the key characteristics of seal bites including substantial loss of skin and blubber, puncture wounds (often repetitive) to the head, tail and flippers, plus series of parallel scratches anywhere on the body left by seal claws. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/65509/original/image-20141125-4228-h2lzqg.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/65509/original/image-20141125-4228-h2lzqg.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/65509/original/image-20141125-4228-h2lzqg.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/65509/original/image-20141125-4228-h2lzqg.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/65509/original/image-20141125-4228-h2lzqg.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/65509/original/image-20141125-4228-h2lzqg.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/65509/original/image-20141125-4228-h2lzqg.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">Seal meal?</span>
<span class="attribution"><span class="source">Johan Krol</span></span>
</figcaption>
</figure>
<p>A flow chart has been produced using these marks to determine if the porpoise was attacked by a seal and if it could have escaped. This will be invaluable to those undertaking autopsies of porpoises in the future. </p>
<p>The majority of confirmed seal attacks are on juveniles. Since many of the porpoise carcasses were found on Dutch bathing and surfing beaches the authors offer up the thought that humans may be at risk.</p>
<p>Perhaps this serves us right, as it seems humans may have triggered this change in seal diet. Along with their close relatives dolphins and whales, porpoises often become entangled in fishing gear and some attacks may simply be seals scavenging trapped porpoises. Having got used to the scavenged fare, the authors speculate that seals may have turned to attacking live porpoise.</p>
<p>Porpoises have a hard life. <a href="http://www.dailymail.co.uk/news/article-2572968/Pictured-Horrific-moment-bottlenose-dolphins-attack-kill-two-porpoises-FUN-cat-mouse-game.html">Even dolphins</a> attack them. They are victims of the fishing industry and subject to an increasing amount of noise from boats, oil rigs and wind turbines. </p>
<p>Now, possibly triggered by our activities, there is yet another pressure on this species: hungry seals.</p><img src="https://counter.theconversation.com/content/34690/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ken Collins 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>It’s one of the big mysteries in my career as a marine biologist. Something lurking in the seas off Britain has been chomping away at local porpoises and none of the usual suspects fit the bill. Now scientists…Ken Collins, Senior Research Fellow, Ocean and Earth Science, University of SouthamptonLicensed as Creative Commons – attribution, no derivatives.