tag:theconversation.com,2011:/au/topics/reef-fish-939/articlesReef fish – The Conversation2022-08-15T15:37:15Ztag:theconversation.com,2011:article/1886762022-08-15T15:37:15Z2022-08-15T15:37:15ZHow to finance marine conservation without harming local communities<p>Subject to <a href="https://www.cell.com/current-biology/fulltext/S0960-9822(21)01198-2">overfishing</a>, marine megafauna – such as sharks, rays, and turtles – are among the world’s most <a href="https://www.iucnredlist.org/resources/summary-statistics">threatened species groups</a>. Somewhat paradoxically, these species also have widespread appeal.</p>
<p>Tourist activities, such as scuba diving place considerable economic value on these species. <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0065051">One study</a> values global manta ray tourism at US$140 million (£116 million) each year.</p>
<p>Marine tourism is often promoted as a more conservation-compatible substitute to unsustainable fishing. However, despite its value, marine tourism <a href="https://www.frontiersin.org/articles/10.3389/fmars.2020.00261/full">rarely contributes directly</a> towards conservation. The economic value of these species is typically extracted by the tourism industry and rarely filters directly into conservation actions. </p>
<p>Coastal communities that depend on marine megafauna for food and income are, in contrast, <a href="https://www.frontiersin.org/articles/10.3389/fmars.2020.00261/full">rarely well placed</a> to benefit from marine tourism. </p>
<p>And subject to restrictive regulations, the costs of marine conservation also often <a href="https://conbio.onlinelibrary.wiley.com/doi/full/10.1111/csp2.494">fall</a> on these communities. <a href="https://conbio.onlinelibrary.wiley.com/doi/full/10.1111/csp2.494">One study</a> estimated, for example, that catch limits on endangered shark species could cost low-income Indonesian fishers up to 17.6% of their annual revenue.</p>
<h2>A ‘beneficiary pays’ approach</h2>
<p>A potential solution to this <a href="https://www.cambridge.org/core/product/identifier/S0030605303000413/type/journal_article">inequity</a> is a “beneficiary pays” conservation approach. </p>
<p>Here, a fee is levied on tourists or tourist-focused businesses. The proceeds are then invested into community-based conservation projects, which provide coastal communities with the resources to facilitate conservation, while supporting their livelihoods.</p>
<p>In a <a href="https://www.sciencedirect.com/science/article/pii/S0921800922002403">recent study</a>, my colleagues and I investigated the feasibility of this approach.</p>
<p>Using an online survey of people with a general interest in travel, we established the willingness of international marine tourists to pay towards community-based shark conservation. Participants were presented with a scenario in which they were at a tropical beach destination. They were also informed of a nearby community highly dependent on catching endangered sharks.</p>
<p>Given this scenario, participants were asked the maximum amount they would pay for a marine conservation fee. The fee, added to the price of marine activities, would directly compensate local fishers for reducing their catch of endangered shark species.</p>
<p>By combining the average willingness-to-pay per person with market data from two popular Indonesian holiday destinations – Lombok and Pulau Weh, both home to several endangered shark species – we estimated how much conservation revenue could be raised annually.</p>
<h2>Wide support for tourism levies</h2>
<p>Our results show wide support for tourism levies. </p>
<p>Survey respondents were willing to pay a daily average of US$10–15 (£8.25–12.37) per person towards community-based marine conservation projects.</p>
<p>This corresponds to US$2.3–6.8 million (£1.9–5.6 million) per year in Lombok and US$300,000–900,000 (£247,000–742,000) per year in Pulau Weh in potential revenue for coastal communities. The lower estimate is based on a levy of US$10 per day and one day of marine activities per tourist, and the upper based on US$15 per day and two days of marine activities per tourist.</p>
<p>These revenues exceed the <a href="https://osf.io/bxzfs/">estimated costs</a> of community-based shark conservation in nearby fisheries. <a href="https://www.instagram.com/kebersamaan_untuk_lautan/">Pilot projects</a> are already ongoing in these communities, whereby fishers are compensated for releasing critically endangered species, with some early success.</p>
<p><div data-react-class="InstagramEmbed" data-react-props="{"url":"https://www.instagram.com/p/CfdtWMIpmB4/","accessToken":"127105130696839|b4b75090c9688d81dfd245afe6052f20"}"></div></p>
<h2>Direct investment</h2>
<p>Marine tourism is an underutilised source of revenue for marine conservation. However, financing mechanisms must be appropriately designed.</p>
<p>Respondents in our study expressed strong preferences for funding environmental NGOs or direct payments to local communities. There was less support for paying a levy to national or local governments. This implies that for marine tourism levies to be successful, the revenues must be openly distributed to locally-run projects.</p>
<p>Our research also found that travellers’ willingness to pay depended on their holiday budget. Therefore, conservation revenue may be higher in luxury destinations and far lower for budget destinations. This highlights the need for mechanisms to be adapted to local contexts and markets.</p>
<p>We would also suggest, based on our findings, that offering information about marine conservation at the “point of sale” may not be needed. We found that existing pro-environmental behaviours led to a greater willingness to pay. Providing information on shark conservation issues directly prior to the survey had little effect on the willingness of participants to pay.</p>
<p>Over 80% of respondents also agreed that they would be more likely to purchase goods and services from environmentally conscious tourism companies. This further raises the possibility that companies who incorporate conservation levies into their prices may even be deemed more attractive by customers.</p>
<p>Reef areas attract about <a href="http://dx.doi.org/10.1016/j.marpol.2017.05.014">70 million tourists</a> annually. If each tourist is willing to pay just US$10 (£8.25) per trip, marine tourism levies could generate at least US$700 million (£580 million) for marine conservation annually, and in doing so ensure that vulnerable coastal communities do not bear the full costs. </p>
<p>Marine tourism levies can become a key financing mechanism for delivering global biodiversity goals and addressing mismatches between the costs and benefits of marine conservation. But only if they are correctly designed. There is a clear opportunity for tourism operators, governments, NGOs, and coastal communities to develop partnerships to ensure the potential of marine tourism levies can be realised.</p><img src="https://counter.theconversation.com/content/188676/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hollie Booth 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 true cost of marine conservation often falls on vulnerable coastal communities. Can a ‘beneficiary pays’ approach protect both endangered species and the communities dependent on them?Hollie Booth, Nature Positive Senior Specialist at The Biodiversity Consultancy, and Post-Doc Research Associate, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1630622021-08-24T14:31:55Z2021-08-24T14:31:55ZHow fear of being eaten might help keep invasive lionfish from taking over reefs<figure><img src="https://images.theconversation.com/files/417460/original/file-20210823-22-1pz2luo.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2618%2C1844&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lionfish are now invading the western Atlantic Ocean, from North Carolina to Brazil. </span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>The fish stared at me, and I stared right back, taking in its tiger-like red and white stripes, its flamboyant, fan-like pectoral fins, and the row of venomous, upright spines along its back. Thin pieces of its flesh swayed ominously on the spikes in the ocean currents. </p>
<p>The lionfish is a striking creature. There is no wonder why it is <a href="https://doi.org/10.1371/journal.pone.0221272">a popular fish in the aquarium trade</a>.</p>
<p>But the lionfish is also infamous, at the centre of <a href="https://doi.org/10.1111/jfb.13544">one of the most well documented and concerning marine fish invasions in history</a>. Large individuals are often bold and will position themselves in a head-down, menacing posture with flaring fins and swaying spines, toward any potential threat, including divers like me.</p>
<p>I was on a reef off Eleuthera Island, in the Bahamas, where I was studying the interactions between native predatory fishes and invasive lionfish.</p>
<p>The lionfish has few natural predators, and its venomous spines pose a major problem for marine managers because they deter potential predators that could naturally control the growth of this invader’s population. I hoped my research might show that at least some predators in the Bahamas could challenge the successful takeover of reefs by lionfish. </p>
<h2>Atlantic under invasion</h2>
<p>Lionfish — a general term often used to describe two species, <em>Pterois volitans</em> and <em>P. miles</em> — are native to the Indian and Pacific oceans where they are mid-level predators on coral reefs, feeding on a variety of crustaceans and small fishes. But they are now invading the western Atlantic Ocean, from North Carolina to Brazil. </p>
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<img alt="A lionfish surrounded by small white and green reef fish." src="https://images.theconversation.com/files/417463/original/file-20210823-27-u4iwh1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/417463/original/file-20210823-27-u4iwh1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/417463/original/file-20210823-27-u4iwh1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/417463/original/file-20210823-27-u4iwh1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/417463/original/file-20210823-27-u4iwh1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/417463/original/file-20210823-27-u4iwh1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/417463/original/file-20210823-27-u4iwh1.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">Lionfish hunt commercially valuable fish like snapper and other reef fish.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
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<p>Lionfish were introduced in the mid-1980s off the coast of Florida, <a href="http://www.doi.org/10.3354/meps266239">where they escaped from home aquariums or were intentionally released</a>. Now spread out along much of the American Atlantic coast, these efficient predators have <a href="https://doi.org/10.1371/journal.pone.0032596">decimated native fish populations on some Caribbean reefs by an average of 65 per cent</a>. And it doesn’t stop there. <a href="https://doi.org/10.1016/j.marpol.2019.02.052">Lionfish are also now invading parts of the eastern Mediterranean</a>.</p>
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<a href="https://theconversation.com/lionfish-the-mediterranean-invasion-of-an-untouchable-and-enigmatic-predator-119199">Lionfish: the Mediterranean invasion of an untouchable and enigmatic predator</a>
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<p>Among its prey are young commercially valuable species like snappers and grunts, meaning lionfish could have a negative impact on reef fisheries in the medium- to long-term. It also <a href="https://doi.org/10.1007/s00338-015-1293-z">eats the critically endangered social wrasse, found only in Belize</a>. It has even <a href="https://doi.org/10.1371/journal.pone.0177179">consumed substantial numbers of a fish species new to science</a>. </p>
<p>They also pose a bit of a problem for recreational dive tourism. </p>
<p>When lionfish numbers grow and native fishes decrease, the esthetic value of coral reefs can drop. One study found that unexperienced divers preferred seeing lionfish on reefs, but <a href="https://doi.org/10.3389/fmars.2017.00138">more experienced divers, who also tend to spend more money diving, did not</a>.</p>
<h2>Protecting groupers</h2>
<p>In 2008, a study found <a href="https://doi.org/10.1007/s00338-008-0372-9">Caribbean groupers, a common and widespread group of medium-to-large sized coral reef fishes, were eating lionfish</a> in the Bahamas. This early evidence gave everyone in the region hope that groupers might be a natural, cheap and relatively easy solution to reducing lionfish numbers and curbing their negative impacts on native fish. One would only have to protect the groupers and let nature do its thing. </p>
<figure class="align-center ">
<img alt="A man prepares lionfish with a knife." src="https://images.theconversation.com/files/417465/original/file-20210823-25-t2ld0s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/417465/original/file-20210823-25-t2ld0s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/417465/original/file-20210823-25-t2ld0s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/417465/original/file-20210823-25-t2ld0s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/417465/original/file-20210823-25-t2ld0s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/417465/original/file-20210823-25-t2ld0s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/417465/original/file-20210823-25-t2ld0s.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">Some regions promote lionfish hunts and chefs have put lionfish on the menus to remove fish from the reefs and to promote awareness among the public.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
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<p>It seemed far <a href="https://doi.org/10.1007/s10530-017-1449-6">more financially feasible and ecologically effective than other strategies like culling</a>, which involves divers plucking lionfish from reefs one by one using pole spears and nets. It would also involve <a href="https://doi.org/10.1086/710254">less work than persuading people to fish and consume lionfish through a commercial fishery</a>. </p>
<p>Later studies, however, produced conflicting evidence. One small-scale, observational study in a marine protected area in the Bahamas showed that <a href="https://doi.org/10.1371/journal.pone.0021510">lionfish abundances tended to decline with increasing abundances of native groupers</a>. Yet a larger study involving three eco-regions within the Caribbean, <a href="https://doi.org/10.1371/journal.pone.0068259">found no relationship between lionfish and grouper abundances</a>.</p>
<p>Both studies searched for correlations between grouper and lionfish abundances in the Caribbean, and both lacked experimental field work. Until now.</p>
<h2>The power of fear</h2>
<p>In a field experiment on coral reef patches around Eleuthera Island, the Bahamas, Isabelle Côté, a professor of marine ecology at Simon Fraser University, and I investigated whether groupers might limit the success of lionfish in more subtle ways. Perhaps the fear of being eaten (called fear effects) or competition for food from similarly sized groupers would limit lionfish survival, or their negative impacts on native species. </p>
<p>Fear effects are common in nature. They occur when prey alter their behaviours in ways that make it difficult for predators to encounter, detect or capture them — but sometimes at a cost. </p>
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<img alt="A grouper and a lionfish." src="https://images.theconversation.com/files/417464/original/file-20210823-21-1dibq99.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/417464/original/file-20210823-21-1dibq99.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/417464/original/file-20210823-21-1dibq99.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/417464/original/file-20210823-21-1dibq99.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/417464/original/file-20210823-21-1dibq99.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/417464/original/file-20210823-21-1dibq99.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/417464/original/file-20210823-21-1dibq99.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">Earlier research suggested that grouper might eat lionfish and help control their growing populations.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
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<p>Although lionfish are typically bold toward other fishes (and human divers), large groupers may evoke fear in smaller lionfish. This might then lead to behavioural changes that make it more difficult for groupers to eat lionfish, but that also disadvantage the lionfish in a way that is beneficial to native species. </p>
<p>We found that <a href="https://doi.org/10.1007/s00338-021-02117-7">small lionfish were more likely to hide at dawn</a> — peak feeding hours — on reefs with high numbers of large groupers. Usually, both <a href="http://hixon.science.oregonstate.edu/files/hixon/publications/026%20-%20Hixon%2091%20Sale%20book/index.pdf">groupers and lionfish take advantage of the low light to hunt</a>, but if lionfish are hiding when they should be hunting, they eat less — good news for the native fish.</p>
<p>Lionfish were also less active during the day on reefs with increasing grouper predator densities. If a lionfish wants a quick snack of unsuspecting prey during daylight hours, it is less likely to do so if it is inactive. Lionfish can’t eat if they’re hiding or inactive, and <a href="https://doi.org/10.1890/07-1671.1">less food can lead to reduced body growth in reef fish</a>.</p>
<h2>Swamped by yellow grunts</h2>
<p>Unfortunately, we didn’t see a change in the abundance of native fish in our study. This might have been due to bad timing. When we went to measure them, the reefs were flooded with hundreds of small, yellow grunts following a major, summer recruitment event, when young fish settle out of the water column onto reefs. Any effect that reduced lionfish foraging may have had on prey fishes could have been swamped by this excess of available food.</p>
<p>So where does this leave us? Large groupers may play a role in reducing lionfish foraging success, but it is unclear whether this effect has any bearing on native prey populations or on lionfish traits that may increase its ability to survive or reproduce, like body size. </p>
<p>Groupers are heavily fished throughout the Caribbean. If they are to have an effect on the lionfish invasion, governments may need to impose stricter regulations that protect more than just one species of grouper.</p>
<p>Groupers may not be the silver bullet that saves coral reefs. Other, potentially more difficult, invasion management strategies like culling, lionfish tournaments and promoting a commercial lionfishery may all be required. We may need to throw everything at this problem.</p><img src="https://counter.theconversation.com/content/163062/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicola Smith received funding from The Bullitt Foundation Environmental Prize and the Organization of American States Academic Graduate Scholarship.</span></em></p>The lionfish has few natural predators, and its venomous spines deter potential predators. But there may still be ways to naturally control the growth of this invader’s population.Nicola S. Smith, Postdoctoral research fellow, Department of Biological Sciences, Simon Fraser UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1531922021-02-04T19:07:22Z2021-02-04T19:07:22ZUnder the moonlight: a little light and shade helps larval fish to grow at night<figure><img src="https://images.theconversation.com/files/381879/original/file-20210202-13-bt8w1j.JPG?ixlib=rb-1.1.0&rect=3%2C572%2C2061%2C1040&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Jeffrey Shima</span>, <span class="license">Author provided</span></span></figcaption></figure><p>At night on any one of hundreds of coral reefs across the tropical Pacific, larval fish just below the sea surface are gambling on their chances of survival.</p>
<p>Our latest <a href="https://royalsocietypublishing.org/doi/full/10.1098/rspb.2020.2609" title="Lunar rhythms in growth of larval fish">research</a> shows the brightness of the Moon could play a major role in that struggle for survival by affecting the availability of prey and keeping predators away.</p>
<p>Understanding how that works could help in fisheries management, specifically the prediction of changes to harvested fish stocks that allow us to anticipate how many adult fish can be taken without destabilising the fishery.</p>
<p>Many fish populations experience boom-and-bust cycles largely because parents routinely produce millions of offspring that have very low, but fluctuating, survival rates.</p>
<p>The large number of larval fish that are produced means any environmental conditions — for example, increased nutrients — that improve survival odds even only marginally can lead to a big influx in the number of surviving offspring.</p>
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<a href="https://images.theconversation.com/files/381889/original/file-20210202-19-1bi8kal.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Several sixbar wrasse swim above a reef." src="https://images.theconversation.com/files/381889/original/file-20210202-19-1bi8kal.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/381889/original/file-20210202-19-1bi8kal.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=383&fit=crop&dpr=1 600w, https://images.theconversation.com/files/381889/original/file-20210202-19-1bi8kal.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=383&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/381889/original/file-20210202-19-1bi8kal.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=383&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/381889/original/file-20210202-19-1bi8kal.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=482&fit=crop&dpr=1 754w, https://images.theconversation.com/files/381889/original/file-20210202-19-1bi8kal.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=482&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/381889/original/file-20210202-19-1bi8kal.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=482&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">Adult sixbar wrasse in courtship.</span>
<span class="attribution"><span class="source">Author?</span>, <span class="license">Author provided</span></span>
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<h2>When the Sun goes down</h2>
<p>In the past we failed to take into account the influences the night may have on fish development.</p>
<p>In our <a href="https://royalsocietypublishing.org/doi/full/10.1098/rspb.2020.2609" title="Lunar rhythms in growth of larval fish">research</a> we found the daily growth rates of the larvae of sixbar wrasse (<a href="https://www.fishbase.se/summary/5643"><em>Thalassoma hardwicke</em></a>) around the island of Mo’orea, in French Polynesia, are strongly linked to phases of the Moon.</p>
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Read more:
<a href="https://theconversation.com/the-viral-wellerman-sea-shanty-is-also-a-window-into-the-remarkable-cross-cultural-whaling-history-of-aotearoa-new-zealand-153634">The viral ‘Wellerman’ sea shanty is also a window into the remarkable cross-cultural whaling history of Aotearoa New Zealand</a>
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<p>Their growth appears to be maximised when the first half of the night is dark and the second half of the night is bright.</p>
<p>Cloudy nights obscure the Moon, and thus allowed us to check our models by contrasting growth on cloudy versus clear nights, which confirmed the effect of moonlight on growth of these fish.</p>
<h2>Phases of the Moon</h2>
<p>We found that on the best nights of the lunar month for sixbars, around the last Quarter Moon when the Moon rises around midnight, larval fish grew about 0.012mm a day more than average.</p>
<p>But on the worst nights, around the first Quarter Moon when the Moon is overhead at sunset and sets around midnight, they grew about 0.014mm a day less than average. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/382161/original/file-20210203-23-2v1p74.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="From First Quarter to Full Moon then Last Quarter." src="https://images.theconversation.com/files/382161/original/file-20210203-23-2v1p74.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/382161/original/file-20210203-23-2v1p74.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=142&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382161/original/file-20210203-23-2v1p74.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=142&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382161/original/file-20210203-23-2v1p74.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=142&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382161/original/file-20210203-23-2v1p74.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=178&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382161/original/file-20210203-23-2v1p74.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=178&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382161/original/file-20210203-23-2v1p74.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=178&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Phases of the Moon from the Southern Hemisphere.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Moon_phases_en.jpg">Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>For a typical larval sixbar of 37.5 days old, that means its growth is 24% more on the best night than on the worst one. This is important, as growth is inextricably linked to survival and ultimately fisheries productivity.</p>
<p>We think the Moon affects larval growth in this way because of how it changes the movements of deeper-dwelling animals, those that migrate into shallow water each night to hunt for food under the cover of darkness.</p>
<p>Zooplankton — potential prey for larval sixbars — respond quickly to the arrival of darkness, and move into the surface water to supplement the diets of sixbars.</p>
<p>Micronekton, such as lanternfishes, which hunt larval fishes, may take much longer to reach surface waters and seek out their prey, due to their migration from much deeper depths.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/381884/original/file-20210202-17-e186t6.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Four graphs showing different phases of the Moon and the amount of predator/prey during each phase." src="https://images.theconversation.com/files/381884/original/file-20210202-17-e186t6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/381884/original/file-20210202-17-e186t6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=685&fit=crop&dpr=1 600w, https://images.theconversation.com/files/381884/original/file-20210202-17-e186t6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=685&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/381884/original/file-20210202-17-e186t6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=685&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/381884/original/file-20210202-17-e186t6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=861&fit=crop&dpr=1 754w, https://images.theconversation.com/files/381884/original/file-20210202-17-e186t6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=861&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/381884/original/file-20210202-17-e186t6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=861&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Four graphs showing the larval fish (in yellow) and the amount of predator (red shading area) and prey (brown shading area) rising to the surface during each phase of he Moon.</span>
<span class="attribution"><a class="source" href="https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2020.2609">Proceedings of the Royal Society B</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>As a consequence, prey availability for sixbars in surface waters may be hindered by early nocturnal brightness while the arrival of predators may be impeded by late nocturnal brightness.</p>
<p>Thus, larval fish grow best when their predators are absent but their prey are abundant — around the last Quarter Moon.</p>
<p>In contrast, around the first Quarter Moon, prey are suppressed but predators are not, leading to the slowest growth. </p>
<p>During the New Moon, when the surface waters remain dark throughout the night, influxes of both prey and predators may be high, with the latter preventing the larval fish from enjoying the increased numbers of prey. </p>
<p>On the other hand, during the Full Moon, when surface waters are well-lit, the movement of prey and predators may be suppressed, reducing the risk to the fish but also eliminating their food.</p>
<h2>Impact on fishing</h2>
<p>More research is needed to quantify these lunar effects on other marine populations. But our findings to date are good news for those working to strengthen fisheries management, given that phases of the Moon are predictable and cloud cover that can modify moonlight is being measured by satellites.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/381886/original/file-20210202-17-152141l.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diver underwater keeping watch on one of the sixbar wrasse fish." src="https://images.theconversation.com/files/381886/original/file-20210202-17-152141l.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/381886/original/file-20210202-17-152141l.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/381886/original/file-20210202-17-152141l.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/381886/original/file-20210202-17-152141l.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/381886/original/file-20210202-17-152141l.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=532&fit=crop&dpr=1 754w, https://images.theconversation.com/files/381886/original/file-20210202-17-152141l.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=532&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/381886/original/file-20210202-17-152141l.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=532&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Observing the sixbar wrasse spawning.</span>
<span class="attribution"><span class="source">Author?</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>This makes the incorporation of moonlight into existing fisheries management models relatively simple.</p>
<p>We think this will have implications around the world, not just in the tropics. This is because the nightly upward movements of deep-water animals is ubiquitous — it is the largest mass migration of biomass on the planet, and it happens everywhere.</p>
<p>The suppressive effect of moonlight on this movement of potential predators and prey is also a global phenomenon.</p>
<p>We evaluated effects of the Moon on growth of larval temperate fish in an earlier <a href="https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecy.2563" title="Moonlight enhances growth in larval fish">study</a> and found a similar effect (moonlight enhanced growth).</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/coral-reefs-climate-change-and-pesticides-could-conspire-to-crash-fish-populations-142689">Coral reefs: climate change and pesticides could conspire to crash fish populations</a>
</strong>
</em>
</p>
<hr>
<p>The effect is stronger and more nuanced in our latest study, most likely because the waters in the tropics are comparatively clear.</p>
<p>Our findings also hint that other factors which affect night-time illumination of the sea may disrupt marine ecosystems. This includes the reflection of artificial lights from coastal cities, suspended sediments in the water column, and changes in cloud cover due to climate change.</p>
<p>In the future, we may be able to harness this extra information to help forecast fish population change to better guide the management and conservation of fisheries around the world.</p><img src="https://counter.theconversation.com/content/153192/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jeffrey Shima receives funding from Royal Society of New Zealand Marsden Fund.
Erik Noonburg, a retired Associate Professor of Biological Sciences at Florida Atlantic University,
contributed to this article</span></em></p><p class="fine-print"><em><span>Craig W. Osenberg receives funding from the US National Science Foundation.</span></em></p><p class="fine-print"><em><span>Stephen Swearer receives funding from Royal Society of New Zealand Marsden Fund. </span></em></p><p class="fine-print"><em><span>Suzanne Alonzo receives funding from the Marsden Foundation and the US National Science Foundation</span></em></p>Young fish need to find food to grow, but avoid being eaten themselves. That dance for survival is linked to moonlight, which has implications for fisheries management everywhere.Jeffrey Shima, Professor of Ecology, Te Herenga Waka — Victoria University of WellingtonCraig W. Osenberg, Professor of Ecology, University of GeorgiaStephen Swearer, Professor of Marine biology, The University of MelbourneSuzanne Alonzo, Professor of Ecology & Evolutionary Biology, University of California, Santa CruzLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1426892020-07-17T11:06:21Z2020-07-17T11:06:21ZCoral reefs: climate change and pesticides could conspire to crash fish populations<figure><img src="https://images.theconversation.com/files/348125/original/file-20200717-23-pdcqm9.jpg?ixlib=rb-1.1.0&rect=0%2C82%2C2500%2C1579&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/surgeon-bank-coral-fish-epulopiscium-121225426">Jose Angel Astor Rocha/Shutterstock</a></span></figcaption></figure><p>Australia barely had time to recover from record breaking fires at the start of 2020 before the Great Barrier Reef experienced its third mass coral bleaching event in the past five years. Only five of these have occurred <a href="https://www.theguardian.com/environment/2020/apr/07/great-barrier-reefs-third-mass-bleaching-in-five-years-the-most-widespread-ever#:%7E:text=The%20Great%20Barrier%20Reef%20has,temperatures%20driven%20by%20global%20heating.&text=Corals%20can%20recover%20from%20mild,are%20more%20susceptible%20to%20disease.">since records began in the 1980s</a>. High water temperatures and marine heatwaves, caused by climate change, are making coral bleaching an almost regular occurrence in some parts of the world. </p>
<p>Coral reefs are among the most vibrant ecosystems on the planet, but they are also very sensitive to stress. Meteorologists predict that 2020 is likely to be the <a href="https://www.theguardian.com/environment/2020/apr/27/meteorologists-say-2020-on-course-to-be-hottest-year-since-records-began#:%7E:text=Meteorologists%20say%202020%20on%20course%20to%20be%20hottest%20year%20since%20records%20began,-Global%20lockdowns%20have&text=This%20year%20is%20on%20course,record%20set%20four%20years%20ago.">hottest year on record</a>, threatening yet more bleaching on reefs around the world. But it’s not just the coral itself that suffers.</p>
<p>Reef fishes exposed to high temperatures tend not to behave normally. Underwater noise and pollutants, such as agricultural pesticides, can have the same effect. Juvenile fish exposed to this kind of stress are less able to identify and <a href="https://phys.org/news/2018-04-fish-ears-man-made-noise-threatens.html">avoid predators</a>. But scientists aren’t sure exactly why this is.</p>
<p><a href="https://www.nature.com/articles/s41467-020-17450-8">In our new study</a>, we found that a double whammy of higher water temperatures and pesticide exposure may be affecting the development of baby reef fish, with consequences for the entire ecosystem.</p>
<h2>Metamorphosis in coral reef fish</h2>
<p>Metamorphosis might bring to mind the transformation a caterpillar undergoes to become a butterfly, but it is also very common in coral reef fishes. After hatching from eggs, most reef fish develop as translucent larvae in the open ocean, before transforming into juvenile fish as they are recruited to their life on the reef. </p>
<p>This journey is a very important transition that is fraught with danger. Many predators like to eat reef fish while they’re in this small and vulnerable stage.</p>
<figure class="align-center ">
<img alt="A translucent larval fish next to a fish at a later stage of development." src="https://images.theconversation.com/files/347729/original/file-20200715-25-1mjqz5k.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/347729/original/file-20200715-25-1mjqz5k.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=198&fit=crop&dpr=1 600w, https://images.theconversation.com/files/347729/original/file-20200715-25-1mjqz5k.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=198&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/347729/original/file-20200715-25-1mjqz5k.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=198&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/347729/original/file-20200715-25-1mjqz5k.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=248&fit=crop&dpr=1 754w, https://images.theconversation.com/files/347729/original/file-20200715-25-1mjqz5k.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=248&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/347729/original/file-20200715-25-1mjqz5k.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=248&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Like most coral reef fish, convict surgeonfish are transparent while larvae (left). During recruitment, they change into something more typically resembling a fish (right).</span>
<span class="attribution"><span class="source">Marc Besson</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>During metamorphosis, fish rapidly develop their eyes, noses and lateral line system, a special set of organs that allows them to detect changes in water pressure. Reef fish rely on these senses to spot and avoid predators. </p>
<p><a href="https://elifesciences.org/articles/27595">Recent studies</a> have shown that the process is regulated by hormones in coral reef fish. So if man-made pressures as diverse as increasing temperatures, underwater noise and pollution can cause juveniles to behave strangely and fail to avoid predators, perhaps it all has something to do with their hormones.</p>
<p>We decided to test this in a lab. We exposed the larvae of the surgeon convict fish to chemical hormones and hormone blockers and found that it directly influenced the development of their eyes, noses and lateral line systems. When fish received a hormone blocker, their sensory systems developed more slowly, they were less able to identify a predator by sight or smell and predators caught them more easily. </p>
<figure class="align-center ">
<img alt="A large tropical fish looking straight ahead." src="https://images.theconversation.com/files/347736/original/file-20200715-35-1bzkzpz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/347736/original/file-20200715-35-1bzkzpz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=699&fit=crop&dpr=1 600w, https://images.theconversation.com/files/347736/original/file-20200715-35-1bzkzpz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=699&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/347736/original/file-20200715-35-1bzkzpz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=699&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/347736/original/file-20200715-35-1bzkzpz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=878&fit=crop&dpr=1 754w, https://images.theconversation.com/files/347736/original/file-20200715-35-1bzkzpz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=878&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/347736/original/file-20200715-35-1bzkzpz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=878&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">High temperatures and pesticides can disrupt sensory development in young fish.</span>
<span class="attribution"><span class="source">Aldine Amiel/Kahi Kai</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The lab tests showed that exposure to a hormone blocker can prevent fish from developing the necessary defences for life on a coral reef. So how might they be faring in the ocean, given that pesticides drain off the land into coastal waters, where these chemicals might <a href="http://www.gbrmpa.gov.au/our-work/threats-to-the-reef/declining-water-quality">disrupt hormones in fish</a>?</p>
<p>In further experiments, we exposed fish to different temperatures and doses of a common agricultural pesticide called chlorpyrifos. Higher temperatures and high levels of the pesticide made fish worse at avoiding predators, but when given extra hormones, the fish recovered their abilities. This shows how climate change and pollution can affect how fish naturally regulate their development, and how important it is for them to be able to metamorphose in a healthy environment.</p>
<p>Hotter water and exposure to pesticides might seem like totally different things, but our results suggest they affect metamorphosis in a similar way. This is worrying, because most coral reef fish species metamorphose early in their lives, and if their environment changes too much, it might endanger entire coral reef communities. </p>
<p>Luckily, our results suggest that these negative effects are mostly felt at higher doses, but they are at the extreme end of what is already being detected on reefs. That means that we still have time, but our habits must change soon.</p><img src="https://counter.theconversation.com/content/142689/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Marc Besson receives funding from Fondation Bettencourt Schueller. </span></em></p><p class="fine-print"><em><span>William Feeney 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>Pesticides and high temperatures can disrupt the development of small coral reef fish by targeting their hormones.William Feeney, Postdoctoral Research Fellow in Evolutionary Ecology, Griffith UniversityMarc Besson, Postdoctoral Research Fellow in Marine Ecology, École pratique des hautes études (EPHE)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1373832020-05-21T20:17:05Z2020-05-21T20:17:05ZMarine heat waves spell trouble for tropical reef fish — even before corals die<figure><img src="https://images.theconversation.com/files/336587/original/file-20200520-152327-r9k34j.jpg?ixlib=rb-1.1.0&rect=81%2C126%2C5898%2C3872&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A school of convict tang (_Acanthurus triostegus_) swim on Kiritimati's dead reefs after the 2015–16 marine heatwave.</span> <span class="attribution"><span class="source">(Kevin Bruce)</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Despite the <a href="https://wwf.panda.org/our_work/oceans/problems/">many challenges facing the world’s oceans</a> today, coral reefs remain strongholds of marine biodiversity. <a href="https://www.sciencedirect.com/science/article/pii/S0960982214016236">Thousands of species of fish</a> of all shapes and sizes call these colourful, complex and economically important ecosystems home. <a href="https://doi.org/10.1038/nclimate3382">Impending ocean warming, however, spells trouble for these fishes</a>.</p>
<p>Ever since the <a href="https://www.icriforum.org/documents/status-of-coral-reefs-of-the-world-2000/">first global coral bleaching event</a> devastated reefs in the late 1990s, scientists have worked to document the effects of these catastrophic phenomena on coral reef fishes. In the wake of severe bleaching, <a href="https://www.mdpi.com/1424-2818/3/3/424">coral mortality often leads to changes in the community of fish that live on the reef</a>: fish that feed on corals decline, while those that feed on algae increase as the latter proliferates. </p>
<p>But what happens to fish during a severe heat stress event — that is, when water temperatures rise, but the corals have not yet bleached and died? It seems that very few scientists have tried to find out. </p>
<p><a href="https://doi.org/10.1002/eap.2124">Our new study</a>, published in <em>Ecological Applications</em>, surveyed reef fish communities before, during and after the 2015–16 El Niño on Kiritimati, a coral atoll in the Pacific Ocean, that is part of the country of Kiribati. Our research suggests that short-term increases in water temperature may have devastating impacts on reef fish populations and the local communities that rely on them.</p>
<h2>Heating up the world’s largest atoll</h2>
<p>Kiritimati, or Christmas Island, is the world’s largest coral atoll — ring-shaped reef — by land mass. The nearest major airport is more than 2,000 kilometres away, in Hawaii. The people who live on Kiritimati are <a href="https://doi.org/10.1016/j.ocecoaman.2016.01.012">highly dependent on reef fish</a> as a source of both food and income.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/336588/original/file-20200520-152349-1wz6wbe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/336588/original/file-20200520-152349-1wz6wbe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/336588/original/file-20200520-152349-1wz6wbe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/336588/original/file-20200520-152349-1wz6wbe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/336588/original/file-20200520-152349-1wz6wbe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/336588/original/file-20200520-152349-1wz6wbe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/336588/original/file-20200520-152349-1wz6wbe.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">A healthy coral reef on Kiritimati, prior to the El Niño in 2015–16.</span>
<span class="attribution"><span class="source">(Kristina Tietjen)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>While the 2015–16 El Niño <a href="https://www.doi.org/10.1126/science.aan8048">wreaked havoc on reefs worldwide</a>, its effects were especially catastrophic around Kiritimati. <a href="https://doi.org/10.1371/journal.pone.0190957">Unprecedented levels of heat stress</a> persisting for 10 straight months led to <a href="https://www.washingtonpost.com/news/energy-environment/wp/2016/04/12/why-dead-coral-reefs-stir-fears-of-dangerous-climate-change/">over 80 per cent coral mortality</a> around the island, but not before triggering a change in the local fish community.</p>
<h2>Stressed-out reef fish</h2>
<p>After just two months of heat stress, reef fish populations around the atoll had plummeted by half. The number of fish species also declined, with some species disappearing entirely. Five species, including the Chevron butterflyfish (<em>Chaetodon trifascialis</em>), which feeds exclusively on live coral, have not been seen since. </p>
<p>One year after the heat wave, however, we found — somewhat surprisingly — that total reef fish biomass and abundance had recovered, rebounding to levels similar to those we’d observed in years prior to the heat wave. This begs the question: What exactly happened during those long, heat-stricken months?</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/336589/original/file-20200520-152338-17yd9op.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/336589/original/file-20200520-152338-17yd9op.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/336589/original/file-20200520-152338-17yd9op.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/336589/original/file-20200520-152338-17yd9op.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/336589/original/file-20200520-152338-17yd9op.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/336589/original/file-20200520-152338-17yd9op.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/336589/original/file-20200520-152338-17yd9op.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/336589/original/file-20200520-152338-17yd9op.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">The pufferfish, <em>Arothron meleagris</em>, one of the many reef fish species on Kiritimati that declined during the heat wave.</span>
<span class="attribution"><span class="source">(Sean Dimoff)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>While severe heat stress can lead to <a href="http://www.int-res.com/abstracts/meps/v401/p233-243/">decreased fitness</a> and even <a href="https://doi.org/10.1111/gcb.12455">mortality</a> in reef fishes, we believe that most of the missing fish sought shelter on the deeper, cooler reefs around the island during the heat wave. Once the heat had subsided, they could have easily returned to the shallows.</p>
<p>Yet the recovery of the reef fish community was not the same across the board. Sites on the atoll nearest to the villages, where the reefs have been heavily affected by dredging, fishing and pollution, had impaired recovery relative to areas of the atoll far from villages where the reefs were nearly pristine prior to the heat wave. </p>
<p>This suggests that local environmental protection could help make reefs more resilient to the ravages of severe ocean warming. While it may not be enough to entice fish to stay put during a severe warming event, high-quality reefs may be more attractive to these fish upon their return.</p>
<h2>A window into the future</h2>
<p>If the reef fish return once the heat stress is over, is their disappearance in the short-term really a big deal? Considering that the survival of <a href="https://www.wri.org/publication/reefs-risk-revisited">millions of people worldwide</a> depends on tropical reef fishes, we believe the answer to this question is a resounding yes.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/336583/original/file-20200520-152344-jc7044.jpg?ixlib=rb-1.1.0&rect=65%2C113%2C3844%2C2880&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/336583/original/file-20200520-152344-jc7044.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/336583/original/file-20200520-152344-jc7044.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/336583/original/file-20200520-152344-jc7044.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/336583/original/file-20200520-152344-jc7044.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/336583/original/file-20200520-152344-jc7044.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/336583/original/file-20200520-152344-jc7044.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 healthy coral reef on Kiritimati, prior to the heat wave.</span>
<span class="attribution"><span class="source">(Kieran Cox)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The impacts of climate change on coral reefs are only <a href="https://www.doi.org/10.1126/science.aaw6974">predicted to worsen</a> in the coming decades. Studying the effects of severe heat stress in the present can serve as a window into the future, foreshadowing the consequences of gradual ocean warming and <a href="https://doi.org/10.1038/s41586-018-0383-9">more frequent and severe marine heat waves</a> that are predicted to occur. </p>
<p>By understanding how fish populations react to elevated water temperatures, we can also attempt to predict and mitigate the effects of ocean warming on highly reef-dependent communities such as those on Kiritimati.</p>
<p>Within the realm of coral reef research, most studies on heat stress to date have focused on the <a href="https://link.springer.com/chapter/10.1007%2F978-94-017-7499-4_8">link between heat stress and coral bleaching</a>, and the <a href="https://doi.org/10.3390/d3030424">knock-on effects of catastrophic bleaching on reef fishes</a>. However, corals are not the only animals affected by the heat stress itself. Unless we intervene to limit climate change globally, we may risk losing not only corals but critically important reef fishes as well.</p><img src="https://counter.theconversation.com/content/137383/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jennifer M.T. Magel receives funding from the Natural Sciences and Engineering Research Council of Canada. </span></em></p><p class="fine-print"><em><span>Julia K. Baum receives funding from the Natural Science and Engineering Research Council of Canada, the Pew Charitable Trusts, National Geographic, and the Rufford Foundation. </span></em></p>Reef fish vanish during marine heat waves, but may bounce back quickly on reefs that have few other environmental stressors.Jennifer M.T. Magel, Research Assistant, Biology, University of VictoriaJulia K. Baum, Professor of Biology, University of VictoriaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/604342016-06-07T15:19:55Z2016-06-07T15:19:55ZHow fish and clean water can protect coral reefs from warming oceans<figure><img src="https://images.theconversation.com/files/125070/original/image-20160603-23288-irvcz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Nice to see you: parrotfishes prey on seaweed, which consume seaweeds that can outcompete, smother or even poison corals. </span> <span class="attribution"><span class="source">Corinne Fuchs</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Hurricanes and waterspouts. Bone-chilling rain and 100 degree Fahrenheit temperatures. Jellyfish and fire coral stings. Broken toes, shoulders, knees and fingers. Entanglements in fishing gear and stranded boats. Cockroaches, mosquitoes and sandflies. Hundreds of SCUBA dives and thousands of hours underwater. And to end it all, mountains of very different kinds of data to integrate. </p>
<p>These are just a few of the challenges we ran up against on our four-year endeavor to ask the the not-so-simple question: “How do three human factors – overfishing, pollution and climate change – intersect to cause the decline of coral reefs?” </p>
<p>By looking at the microbial communities that live on corals, our research uncovered a crucial role that fishes play in protecting coral reefs. We also discovered that these fishes together with clean water may be a vital buffer against the coral disease and decline caused by climate change-induced warming ocean waters. </p>
<h2>Coral reef decline and human impacts</h2>
<p>You may have seen that the plight of the world’s coral reefs, pinnacles of marine biodiversity, has been in the news a lot lately. </p>
<p>Currently, <a href="https://www.ncdc.noaa.gov/teleconnections/enso/indicators/sst.php">El Niño-driven increases</a> in ocean temperatures are causing a third worldwide <a href="http://www.noaa.gov/el-ni%C3%B1o-prolongs-longest-global-coral-bleaching-event">coral bleaching event</a>. Australia’s Great Barrier Reef, one of most protected and largest coral reefs in the world, may lose <a href="https://theconversation.com/how-will-the-barrier-reef-recover-from-the-death-of-one-third-of-its-northern-corals-60186">a third of all its corals</a>. Jarvis, a remote U.S.-protected island, is suffering an unimaginable <a href="http://mashable.com/2016/06/01/coral-death-jarvis-island/#mwd01_FOGPqD">90 percent coral mortality</a>. </p>
<p>While this recent bad news for reefs is eye-catching, coral reefs have been in trouble for a long time. Many reefs around the world have seen gradual declines in corals over the past two to three decades. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/125174/original/image-20160603-11598-1qufuo6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/125174/original/image-20160603-11598-1qufuo6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/125174/original/image-20160603-11598-1qufuo6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/125174/original/image-20160603-11598-1qufuo6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/125174/original/image-20160603-11598-1qufuo6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/125174/original/image-20160603-11598-1qufuo6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/125174/original/image-20160603-11598-1qufuo6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/125174/original/image-20160603-11598-1qufuo6.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">Scientists sampled the microbial community, or microbiome, around coral reefs to gauge the global and local factors that affect reef health.</span>
<span class="attribution"><span class="source">Becky Vega Thurber</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The decline in corals has many culprits, but they can be classified as two major kinds, local and global stressors. Local stressors involve aspects of human activity that impact reefs on a small regional scale, while global stressors can impact reefs over the entire planet. Local stressors are things like overfishing, pollution and sedimentation from coastal development; they may kill corals all by themselves. </p>
<p>But these local factors never occur in a vacuum. It is likely these local human impacts combine with the ubiquitous ongoing global stressors such as warming oceans and ocean acidification that drive the huge bleaching events we are witnessing today. Yet although we know they occur simultaneously, scientists have rarely investigated the effects of these combined local and global stressors on coral reefs, outside of simplified and unrealistic lab-based experiments that are generally short in duration. </p>
<p>Also, most coral reef research has emphasized the effects of these human stressors on the conspicuous animals and plants that live on a coral reef. In our study, we chose to focus on the microscopic marine life and its role in coral health.</p>
<p>Over the last two decades, scientists have come to understand that all multicellular organisms have evolved with a variety of microorganisms. Much like the microbes that live on and in healthy humans, this “microbiome” of corals helps gather important nutrients and minerals and fight off infection from pathogens. Major changes in the microbiome, in humans, corals, or other organisms, are thought to be detrimental because they can switch a system from a healthy “stable” state to a diseased one. </p>
<p>Thus, we (a coral microbiologist and marine community ecologist) sought to combine the expertise and field work experience of our labs to test the effects of both local and global stressors on corals as well as their microbiomes. </p>
<p>Our reasoning was that by physically changing conditions on areas of reef over the long term, we could monitor what would occur naturally in the system across seasons, and also see how effects at one level of complexity (macroorganisms – that is, the corals) transcended down to another level of complexity (microorganisms). </p>
<h2>Vital role of herbivorous fishes</h2>
<p>We tackled these questions by running a three-year field experiment that mimicked overfishing (using <a href="https://www.unols.org/sites/default/files/SessionIV_Cattrijsse_Francisco.pdf">fish-exclusion cages</a>) and nutrient pollution (via the addition of common garden fertilizer) on a coral reef in the Florida Keys, U.S. To do this we had to build and maintain the experiment underwater for three years, which required continuous upkeep of our cages and resupply of the nutrients every few weeks. We closely monitored the health and growth of corals and seaweeds in our experiment four times a year and evaluated the microbiomes of about 80 corals monthly. </p>
<p>Using this experimental design, we wanted to examine how two of the most common stressors on reefs – overexploitation of important species like herbivorous fishes (i.e., fishes that eat seaweeds) and nutrient pollution – affect the microbes that live on corals and, ultimately, the health of corals. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/125171/original/image-20160603-11585-si3f08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/125171/original/image-20160603-11585-si3f08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/125171/original/image-20160603-11585-si3f08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/125171/original/image-20160603-11585-si3f08.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/125171/original/image-20160603-11585-si3f08.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/125171/original/image-20160603-11585-si3f08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/125171/original/image-20160603-11585-si3f08.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/125171/original/image-20160603-11585-si3f08.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">To study the effects of nutrient pollution and fish populations on corals, the researchers maintained a test site for three years on the Florida Keys.</span>
<span class="attribution"><span class="source">Rebecca Vega Thurber</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Lots of previous work shows that herbivorous fishes, especially <a href="http://voices.nationalgeographic.com/2014/07/02/to-save-coral-reefs-start-with-parrotfish/">parrotfishes</a>, are important for helping corals reproduce, grow and survive because they consume seaweeds that can outcompete, smother or even poison corals. </p>
<p>Our work reinforced that these herbivorous fishes protect reefs by preventing coral-seaweed competition. But we also showed that the loss of these fishes ultimately led to the subsequent disruption of the coral microbiome. </p>
<p>When we removed herbivorous fishes from reefs, coral-seaweed competition increased, which led to declines of some of the beneficial bacteria on corals, including bacteria that produce antibiotics to keep harmful pathogenic bacteria at bay. </p>
<p>Importantly, the presence of herbivorous fishes appeared to buffer some of the negative effects of ocean warming on corals. We knew this because thermal stress led to the disruption of coral microbiomes and coral death only after herbivorous fishes had already been removed. In other words, during the warmest summer and fall months of the year, 95 percent of corals in areas with abundant fishes survived and in fact grew. But if we removed fishes, almost 40 percent of corals succumbed to seaweed competition and thermal stress and died. </p>
<h2>Nutrient pollution turns fishes into coral killers</h2>
<p>Although parrotfishes are important herbivores that help keep reefs clean of seaweeds, many of them periodically supplement their diets by biting corals. In our experiment 100 percent of the corals survived these periodic bites just fine under low nutrient conditions, demonstrating that parrotfishes are an overwhelmingly positive force for helping corals persist on reefs. </p>
<p>One of the most surprising and perhaps worrisome elements uncovered by our study was how nutrient pollution – such as from agricultural runoff or sewage discharge – changed the impact of parrotfish bites on corals. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/125172/original/image-20160603-8272-z42gqr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/125172/original/image-20160603-8272-z42gqr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/125172/original/image-20160603-8272-z42gqr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/125172/original/image-20160603-8272-z42gqr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/125172/original/image-20160603-8272-z42gqr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/125172/original/image-20160603-8272-z42gqr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/125172/original/image-20160603-8272-z42gqr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/125172/original/image-20160603-8272-z42gqr.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">Algae compete with coral for resources, so algae-eating fishes can help prevent coral health and death.</span>
<span class="attribution"><span class="source">Rebecca Vega Thurber</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>In the presence of nutrient pollution, 66 percent of corals died after being bitten by parrotfishes. These corals also showed an increase in pathogenic bacteria at the expense of beneficial bacteria following parrotfish bites, possibly leading to coral mortality. The parrotfish wounds likely allowed a space for colonization by new bacteria and then the excess nutrients allowed unregulated growth of these new pathogens. </p>
<p>It is important to note that the parrotfishes here are not the problem. The nutrient pollution is the problem as it changes the nature of a normally beneficial interaction between species on these reefs. This finding is especially concerning as it suggests that even on reefs where parrotfishes are protected from fishing, a common management practice to protect reefs, corals may still be in peril if pollution is not also kept in check. </p>
<h2>What do we do to save reefs?</h2>
<p>Our work suggests that managing reefs at the local level by protecting important fish species and minimizing pollution can help prevent coral death. Even during the most warmest periods of the year, when temperatures were most stressful, we saw little coral mortality in places where there were abundant fishes and low levels of nutrients. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/125175/original/image-20160603-11611-1uovl5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/125175/original/image-20160603-11611-1uovl5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/125175/original/image-20160603-11611-1uovl5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/125175/original/image-20160603-11611-1uovl5f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/125175/original/image-20160603-11611-1uovl5f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/125175/original/image-20160603-11611-1uovl5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/125175/original/image-20160603-11611-1uovl5f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/125175/original/image-20160603-11611-1uovl5f.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">A diseased coral on the test site.</span>
<span class="attribution"><span class="source">Becky Vega Thurber</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Possibly, protecting fishes and minimizing pollution will help protect corals from pathogenic bacteria that kill corals during stressful thermal events. This is especially important in an era of global climate change where ocean temperatures are gradually rising. Our work suggests there is hope for the future of coral reefs. </p>
<p>There is little we can do about the impacts of massive El Niños on coral reefs. These are global anomalies out of our control. But, abundant fishes and clean water may be key to helping coral reefs survive increasingly stressful normal ocean temperatures – at least in the near term. In the long term, to ensure the persistence of coral reefs, curbing carbon emissions and slowing down the rapidly changing climate is essential.</p><img src="https://counter.theconversation.com/content/60434/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rebecca Vega Thurber receives funding from the National Science Foundation, NIH, and NOAA. </span></em></p><p class="fine-print"><em><span>Deron Burkepile receives funding from the U.S. National Science Foundation and the National Oceanic and Atmospheric Administration. </span></em></p>A combination of factors – pollution, disease and overfishing – is harming corals but scientists have found clues to effective treatment by studying corals’ microbiome.Rebecca Vega Thurber, Associate Professor of Microbiology, Oregon State UniversityDeron Burkepile, Associate Professor of Ecology, University of California, Santa BarbaraLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/393822015-05-27T20:05:07Z2015-05-27T20:05:07ZWe’ve only monitored a fraction of the Barrier Reef’s species<p><em>This long-read article is part of a <a href="https://theconversation.com/au/topics/great-barrier-reef-threats-series">series</a> examining in depth the various threats to the Great Barrier Reef.</em></p>
<p>When the Great Barrier Reef was first <a href="http://whc.unesco.org/en/list/154">placed on the World Heritage List in 1981</a>, it was recognised as being home to a huge diversity of species, many of them threatened. Conserving the reef’s habitats would therefore be a great way to protect many different species all at the same time.</p>
<p>Naturally, some of these thousands of species have attracted more attention than others. Generally these are large animals with high tourism value – often called the “charismatic megafauna” – such as marine mammals, turtles, sea snakes, sharks, rays and seabirds. Many of these species are listed as either <a href="http://www.environment.gov.au/biodiversity/threatened/species">threatened</a> or <a href="http://www.environment.gov.au/epbc/what-is-protected/migratory-species">migratory</a> under Australia’s environmental legislation.</p>
<p>Yet this hardly scratches the surface. Even counting only vertebrates, the Great Barrier Reef (GBR) boasts a diversity of species (see page 23 onwards <a href="http://www.gbrmpa.gov.au/cdn/2014/GBRMPA-Outlook-Report-2014/">here</a>) that can be found in few other places on the planet. It features 1,625 species of bony fish, six of the seven marine turtle species, 30 whale and dolphin species, dugong, 20 breeding seabird species, and some 136 species of sharks and rays. </p>
<p>There are also hugely valuable places such as Raine Island, the world’s largest breeding location for green turtles, which also hosts breeding colonies of 14 seabird species and provides habitat for up to 20 shark and ray species.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/83060/original/image-20150527-25080-orhlb7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/83060/original/image-20150527-25080-orhlb7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/83060/original/image-20150527-25080-orhlb7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/83060/original/image-20150527-25080-orhlb7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/83060/original/image-20150527-25080-orhlb7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/83060/original/image-20150527-25080-orhlb7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/83060/original/image-20150527-25080-orhlb7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/83060/original/image-20150527-25080-orhlb7.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">The Great Barrier Reef is home to some 1,600 species of bony fish.</span>
<span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File%3AReef2172_-_Flickr_-_NOAA_Photo_Library.jpg">Eric Johnson/NOAA/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Yet of these thousands of species, we only have data on population trends for a small few, and most species have never been assessed. There are nine species or species groups of marine vertebrates in the GBR – <a href="http://www.gbrmpa.gov.au/cdn/2014/GBRMPA-Outlook-Report-2014">six are rated as being in poor condition and four have deteriorated</a> since 2009. </p>
<p>The lack of specific data makes it hard to work out which species will be vulnerable to human-generated risks, and to decide on policies to safeguard them. And of the ones that have been assessed, the news is a mixed bag of good and not-so-good.</p>
<h2>Good news stories</h2>
<ul>
<li><p><strong>Humpback whales</strong> were hunted to near extinction in eastern Australia during the 1950s and early 1960s. Since whaling was banned in the early 1960s the population has recovered by an estimated 11% per year, and humpback and dwarf minke whales now support a multimillion-dollar whale-watching industry (see page 32 of the <a href="http://www.gbrmpa.gov.au/cdn/2014/GBRMPA-Outlook-Report-2014/">GBR Outlook Report</a>).</p></li>
<li><p><strong>Loggerhead turtles</strong> breeding in Queensland declined between the 1980s and 2000s as they were hit hard by <a href="http://www.austurtle.org.au/SeaTurtleBiology/loggerhead_Linnaeus.pdf">egg predation and fishing bycatch</a>. Combinations of land based-management, protected area designations and fisheries regulations (such as the 2001 requirement for turtle excluder devices) led to population recovery, although it has still not regained its original level.</p></li>
<li><p><strong>Reef shark</strong> populations have <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0106885">declined in some areas</a>, probably as a result of previous fishing pressures. However, there are early indications of recovery for some species since the rezoning of the GBR and fisheries management changes introduced in 2004. The public has also shown increasing awareness of the need for and value in sustaining healthy shark populations.</p></li>
</ul>
<h2>Sad news stories</h2>
<ul>
<li><p><strong>Hawksbill turtles</strong> on the northern GBR are declining by around 3% per year. The key threats are international turtle hunting, and predation of eggs on Australian islands by native and introduced fauna. Without action, the population is <a href="http://www.austurtle.org.au/SeaTurtleBiology/hawksbill_Linnaeus.pdf">forecast to decline by more than 90% by 2020</a>.</p></li>
<li><p><strong>Most sawfishes</strong> and the speartooth shark have <a href="http://elibrary.gbrmpa.gov.au/jspui/bitstream/11017/2952/1/gbrmpa-VA-Sharks_Rays-11-7-12.pdf">seriously declined</a> in abundance and distribution along the Queensland coast, with some species such as the green sawfish facing potential localised extinctions. Although these species are listed as protected species, they continue to be threatened by fishing and habitat loss and degradation.</p></li>
<li><p><strong>Inshore dolphins</strong> such as the Australian snubfin and Indo-pacific humpback live in small, often isolated, local populations around the coastal areas of the GBR. Although there are no population size estimates for either species they are believed to be in decline and under considerable risk from human activities. </p></li>
<li><p><strong>Dugong</strong>, despite being more abundant in the Torres Strait than anywhere else on Earth, are thought to be in decline in the southern GBR, according to <a href="https://theconversation.com/dugongs-are-safer-in-torres-strait-than-townsville-13552">aerial surveys</a>, and there are concerns that declining sea grass abundance coupled with fisheries and boating related mortality are affecting the population.</p></li>
</ul>
<h2>Conserving homes and habitats</h2>
<p>Rather than focus on individual species, it is perhaps easier to look at the broad habitat types where they live. The different habitats that cover the GBR World Heritage Area include islands, beaches and coastline, seagrass meadows, coral reefs, mangroves, the lagoon floor, shoals, halimeda banks, continental slope and open waters. </p>
<p>The GBR Marine Park Authority’s <a href="http://www.gbrmpa.gov.au/managing-the-reef/great-barrier-reef-outlook-report">Outlook Report</a> states that the condition of five of the ten habitat groups have deteriorated between 2009 and 2014, and for three habitats rated as “good”, their condition was inferred on the basis of limited evidence. Each of these habitats is important for many of the GBR’s most recognised species.</p>
<p>In particular, there have been <a href="http://www.gbrmpa.gov.au/cdn/2014/GBRMPA-Outlook-Report-2014/">well-documented declines in seagrass and hard coral cover</a> across the World Heritage Area, particularly in the southern inshore region of the GBR. Additionally, coastal, estuarine and lagoon floor habitats are also affected by impacts from land-use changes such as <a href="http://www.sciencedirect.com/science/article/pii/S0308597X15000792">coastal modification</a>. Restoring the condition to these habitats is complicated and will take a long time. What’s more, when habitats change we have little idea of the longer-term flow-on consequences for many species. </p>
<p>There are still crucial unanswered questions: how do seagrass seeds disperse along the coast and between coastal bays? What is the abundance, distribution and status of key species (and new ones yet to be discovered)? How and why do coastal species move within and between coastal habitats and coral reefs? </p>
<p>How does bottom-trawling affect seafloor invertebrate species and the flow on impacts to turtles? What is the impact of high seas and International fisheries on the GBR’s marine turtles? How will marine mammals and other vertebrates react to underwater noise from human activities?</p>
<h2>What can be done?</h2>
<p>The Commonwealth and Queensland governments’ <a href="http://www.environment.gov.au/marine/gbr/long-term-sustainability-plan">Reef 2050 Long-Term Sustainability Plan</a>, released earlier this year, is big on ambition but low on detail. Targets are <a href="https://theconversation.com/cloudy-issue-we-need-to-fix-the-barrier-reefs-murky-waters-39380">well defined for water quality</a>, having been the subject of much discussion. But for marine vertebrates and their habitats the targets are often generic, and there is no guarantee that there will be enough resources to do the necessary monitoring to make them any better.</p>
<p>Yet we believe there are several things that can be done. Several of the threatened and declining species are migratory, so one thing we can do is strengthen international cooperation through jointly funded conservation projects. We should also strengthen Indigenous partnerships for research and management, not just in the World Heritage Area but in the neighbouring Torres Strait and southeast Queensland. </p>
<p>We need to <a href="http://www.sciencedirect.com/science/article/pii/S0959378011001427">strengthen the transfer of knowledge</a> between groups doing work on the ground and people in Government who make decisions. There also needs to be concerted effort and political will focused on reviving the integrated planning and management schemes designed to manage and protect the coastal ecosystems that drive and support coastal and reef dwelling species. </p>
<p>From the sheer volume of media discussion about issues such as the Abbot Point port redevelopment, it could be inferred that the people are uncertain about the government’s ability to safeguard the reef’s outstanding value. Community attitudes and support are vital for a healthy reef, and we believe that a concerted effort is needed to restore community confidence and engage the community in conservation efforts.</p>
<p>Meanwhile, we need to identify the species of highest priority. For each species or group of species we then need to understand the threats, work out how to manage them, and properly evaluate the effectiveness of management actions put in place to protect them. </p>
<p>It is unlikely that sufficient resources will be available to address each individual threat for each species or multi-species group, so we need to develop tools which allow decision makers to determine priority actions which when complete provide best conservation bang for buck. </p>
<p>Marine parks work, but are they generally too small to protect mobile or migratory species, so we will need to work out how to conserve species on larger scales. </p>
<p>Monitoring marine populations and habitats is always challenging, especially in near-shore regions with <a href="https://theconversation.com/cloudy-issue-we-need-to-fix-the-barrier-reefs-murky-waters-39380">cloudy water</a>, but if we are to save the valued animals of the Great Barrier Reef, we will need research, results, and a solid plan with realistic priorities on which we can rely on to obtain the best conservation outcomes.</p><img src="https://counter.theconversation.com/content/39382/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Hamann receives funding from the Australian Government's Marine and Tropical Sciences Research Facility and the National Environmental Research Program. He is affiliated with James Cook University.</span></em></p><p class="fine-print"><em><span>Andrew Chin receives funding from the Australian Government Fisheries Research and Development Corporation, and is affiliated with the Center for Sustainable Tropical Fisheries and Aquaculture at James Cook University. He is an executive officer of the Oceania Chondrichthyan Society, a scientific organisation promoting the research and sustainable use of sharks and rays.</span></em></p>The Great Barrier Reef is home to some 1,600 species of bony fish, 130 sharks and rays, and turtles, mammals and more. Most have had no population monitoring, meaning we don’t know how well they are faring.Mark Hamann, Senior Lecturer in Environmental Science (marine focus), James Cook UniversityAndrew Chin, Research Fellow, Centre for Sustainable Tropical Fisheries and Aquaculture, James Cook UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/402132015-04-17T10:13:59Z2015-04-17T10:13:59ZMeasuring coral reef fishes by taking humans out of the picture<figure><img src="https://images.theconversation.com/files/78296/original/image-20150416-5663-1w40pgw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Coral reefs and associated fisheries are of vital social, cultural and economic importance.</span> <span class="attribution"><span class="source">Noah Pomeroy</span>, <span class="license">Author provided</span></span></figcaption></figure><p>We are living in the Anthropocene, a period where humans are the dominant force on Earth’s natural systems. Coral reef ecosystems are no exception. </p>
<p>Widely known for their striking beauty and diversity, coral reefs also have great social, cultural and economic importance. At human-populated islands, small-scale and subsistence coral reef fisheries are often vital sources of protein and income. </p>
<p>However, it is widely recognized that even relatively low levels of fishing can have large impacts on coral reef fish stocks.</p>
<p>How can scientists effectively measure the status and therefore sustainability of coral reef fish populations? One would think that an isolated reef ecosystem shielded from the influence of people would provide an ideal benchmark against which other coral reefs – and their productivity as sources of fish – can be compared. But in a <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0120516">recent study</a>, we found that it is not that simple.</p>
<p>Using data collected by scientific divers at nearly 2,000 sites at islands and atolls across the western-central Pacific, we developed a method for separating human from other environmental factors to assess reef fish status. We found that not all coral reef areas have the same ability to sustain stocks of fish, and what constitutes “natural” varies substantially among locations.</p>
<h2>Getting a baseline</h2>
<p>A prerequisite for effective coral reef fisheries management is to know how the current status of the ecosystem compares to its ‘pristine’ state. In other words, what would local fish stocks be like if humans had not affected the system at all? For coral reef fisheries, estimating pristine reef fish biomass has been difficult. </p>
<p>Unsurprisingly, where you have <a href="http://dx.doi.org/10.1371/journal.pone.0001548">more humans</a>, you tend to get <a href="http://dx.doi.org/10.1155/2011/826234">fewer</a> <a href="http://www.int-res.com/articles/meps2002/230/m230p253.pdf">fish</a>. Yet to compare a remote reef, distant from human impacts, directly with a populated one can be misleading because it assumes that what is normal or natural for one area applies directly to other areas. Instead, each area is under the influence of environmental factors that operate independently of human influence.</p>
<p>We investigated the relative influence of environmental variation and human impacts on groups of reef fish assemblages. The data set used is a culmination of more than 2,000 hours of underwater visual surveys conducted by NOAA scientists and scuba divers for the <a href="http://www.pifsc.noaa.gov/cred/">Pacific Reef Assessment and Monitoring Program</a> (RAMP).</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/78293/original/image-20150416-30509-twpti5.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/78293/original/image-20150416-30509-twpti5.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/78293/original/image-20150416-30509-twpti5.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/78293/original/image-20150416-30509-twpti5.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/78293/original/image-20150416-30509-twpti5.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/78293/original/image-20150416-30509-twpti5.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/78293/original/image-20150416-30509-twpti5.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">Pacific RAMP divers conducting an underwater visual survey of coral reef fishes.</span>
<span class="attribution"><span class="source">Paula Ayotte</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The Pacific RAMP is one of the world’s largest coral reef monitoring efforts, and it is unique for implementing standardized methods and sending core survey divers throughout coral reefs at nearly 40 US and US-affiliated Pacific islands and atolls. The Pacific RAMP has being monitoring coral reefs of the western central Pacific for 15 years, and scientific scuba divers on the fish team are required to know over 600 species of coral reef fish. Over this period, the fish team has counted and sized <a href="https://pifscblog.wordpress.com/2015/04/09/4999999-fish/">five million coral reef fish</a>! </p>
<p>The islands monitored span a wide range of potential human impact from large population centers, such as Oahu, Maui and Guam, to some of the most remote and pristine coral reefs in the world, including Rose Atoll, the Pacific Remote Islands Marine National Monument and the Northwestern Hawaiian Islands. We paired this unique survey data set with satellite-derived estimates of the environmental conditions at each reef location, including sea surface temperature, wave energy and oceanic productivity – all environmental factors that can influence the composition and abundance of coral reef assemblages.</p>
<p>Consequently, we were able to separate the variability in coral reef fish abundance due to changes in large-scale environmental conditions from human-induced variability. By doing this, we were then able to predict what the fish community would be in the absence of humans. </p>
<h2>Clear human impact</h2>
<p>Consistent with previous findings, we documented sharp declines in reef fish biomass even at very low estimates of human population density. However, the absence of humans from remote, uninhabited reef areas in the Pacific was not always associated with spectacularly high reef fish abundance. Rather, differences were strongly associated with variation in background oceanic productivity.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/78123/original/image-20150415-31660-a5dy2p.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/78123/original/image-20150415-31660-a5dy2p.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/78123/original/image-20150415-31660-a5dy2p.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/78123/original/image-20150415-31660-a5dy2p.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/78123/original/image-20150415-31660-a5dy2p.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=567&fit=crop&dpr=1 754w, https://images.theconversation.com/files/78123/original/image-20150415-31660-a5dy2p.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=567&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/78123/original/image-20150415-31660-a5dy2p.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=567&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Coral reefs at populated islands (right hand side, with islands order from low to high human population numbers) have fewer coral reef fish than uninhabited and remote areas (left hand side, with islands ordered from high to low oceanic productivity (CHL)). There exists great variability in the expected reef fish biomass by site that is largely due to natural differences in oceanic productivity. The grey bars are predicted fish biomass in the absence of human impacts.</span>
<span class="attribution"><span class="source">williams/plosonepaper</span></span>
</figcaption>
</figure>
<p>Specifically, areas of high oceanic productivity – that is, reefs in areas of upwelling where cooler, nutrient-rich water is drawn up from the deep to these shallow water habitats – had two to four times the biomass observed in less productive areas.</p>
<p>What this means is that no one reef can be assumed the same in its ability to sustain large reef stocks. So using a remote reef in a highly productive region could well be a misleading benchmark toward which fishery managers might strive.</p>
<p>Controlling for the spatial variability in reef fish biomass that is due to locally dependent environmental factors, we then projected what biomass one would expect, given the local context, but in the absence of humans (grey bars in the graph above). The findings were stark, with an estimated 20%-78% reduction in reef fish biomass in the lightly to more densely human populated areas.</p>
<p>The implications of this work are twofold. Firstly, due to the natural variability among this broadly similar habitat type, coral reefs differ in their capacity to sustain a high level of fish biomass, implying that there is no single target for what a healthy reef should look like.</p>
<p>Secondly, our results confirmed that even very low levels of human presence are associated with dramatic declines in reef fish abundance. This suggests that fully protected no-take zones would be necessary to maintain coral reef communities in something that resembles their natural, pristine state. </p>
<p>A related and <a href="http://www.nature.com/nature/journal/v520/n7547/full/nature14358.html">recent global study</a> that also heavily relied upon the Pacific RAMP data concludes that 83% of the world’s reefs have reef fish biomass that is half or less than half of their natural carrying capacity. </p>
<p>This groundbreaking study, the first to provide a global benchmark estimate of pristine fish biomass, estimated a recovery time of between 35 and 60 years if fishing was to stop in areas where it now occurs. For most locations, anything approaching full recovery will require prolonged and effective enforcement of fishery restrictions. </p>
<p>Ultimately, reef fish biomass targets must be a societal rather than scientific choice. These recent studies provide the basis for properly understanding the extent of anthropogenic depletion of coral reef fishes, and as such, they will allow such choices to be made in an informed manner.</p><img src="https://counter.theconversation.com/content/40213/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Adel Heenan receives funding from NOAA Coral Reef Conservation Program.</span></em></p><p class="fine-print"><em><span>Ivor D Williams receives funding from the NOAA Coral Reef Conservation Program.</span></em></p>Scuba-diving scientists devise method for gauging the health of coral reefs – a vital ecosystem for keeping fisheries sustainable for people.Adel Heenan, Affiliate researcher, National Oceanic and Atmospheric AdministrationIvor D. Williams, National Oceanic and Atmospheric AdministrationLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/390532015-04-09T20:39:28Z2015-04-09T20:39:28ZClimate change can tip the gender balance, but fish can tip it back<figure><img src="https://images.theconversation.com/files/75457/original/image-20150320-2158-sm0pug.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Climate change is affecting gender ratios in fish, and could hamper their ability to return to a 50:50 balance.</span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>As the world warms, it is crucial to understand how animals will respond to and cope with rising temperatures. Some species might be relatively unaffected by climate change, while others may be seriously disrupted. </p>
<p>One vital aspect is how populations maintain their numbers over time through reproduction. It might seem obvious, but an important component of successful reproduction is having the correct ratio of males and females ready to breed within the population. </p>
<p>Animals have evolved a number of different strategies to achieve and maintain the the optimal ratio, although some of these are dependent on the temperature in the ambient environment. </p>
<p>In some species, for example, the gender that juveniles become is influenced by temperatures experienced during early development. This is known as “temperature sex determination”, and is seen in a broad range of animals including turtles, alligators, lizards and fish. </p>
<p>Yet there is concern that global warming poses a threat to entire populations of these animals because of the effect of warming on the gender ratio of juveniles, which has a knock-on effect on breeding adults in the population. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/77444/original/image-20150409-15223-1nrhogc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/77444/original/image-20150409-15223-1nrhogc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/77444/original/image-20150409-15223-1nrhogc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=311&fit=crop&dpr=1 600w, https://images.theconversation.com/files/77444/original/image-20150409-15223-1nrhogc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=311&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/77444/original/image-20150409-15223-1nrhogc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=311&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/77444/original/image-20150409-15223-1nrhogc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=391&fit=crop&dpr=1 754w, https://images.theconversation.com/files/77444/original/image-20150409-15223-1nrhogc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=391&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/77444/original/image-20150409-15223-1nrhogc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=391&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">If water temperatures warm over the Great Barrier Reef, then it could negatively impact breeding in some species of fish.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Out of balance</h2>
<p>For many animals, including fish, a warmer environment means fewer females develop. Even relatively small increases in developmental temperatures – just 1.5°C above normal summer temperatures – can reduce the proportion of female offspring by more than 30%.</p>
<p><a href="http://link.springer.com/article/10.1007%2Fs10682-006-0003-2">Previous research</a> has <a href="http://aerg.canberra.edu.au/library/sex_general/2000_Bragg_etal_nest_selection_gecko_tsd.pdf">investigated</a> how parents can change the timing of breeding or move the location and depth of their nest to compensate for warming. For example, lizards can select nest locations with differing amounts of sunlight to obtain the correct nest temperature.</p>
<p>My colleague and I investigated the ability of parents to adjust the sex of their offspring back to the optimal ratio through other non-behavioural means.</p>
<p>We reared three generations of a marine fish, the <a href="http://fishesofaustralia.net.au/home/species/311">Spiny Chromis</a> coral reef fish, and found that when parents develop from hatching at elevated temperatures, they can adjust their offspring gender back to the ideal 50:50 ratio. This phenomenon is called “transgenerational plasticity”.</p>
<p>We were able to show that the gender balance of offspring was restored when parental fish were reared at 1.5°C temperature for their entire life and for two subsequent generations. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/77445/original/image-20150409-15244-td2gvw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/77445/original/image-20150409-15244-td2gvw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/77445/original/image-20150409-15244-td2gvw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=461&fit=crop&dpr=1 600w, https://images.theconversation.com/files/77445/original/image-20150409-15244-td2gvw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=461&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/77445/original/image-20150409-15244-td2gvw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=461&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/77445/original/image-20150409-15244-td2gvw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=579&fit=crop&dpr=1 754w, https://images.theconversation.com/files/77445/original/image-20150409-15244-td2gvw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=579&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/77445/original/image-20150409-15244-td2gvw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=579&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Some fish can correct for the effects of higher temperatures on sex ratio, but only to an extent.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Limited resilience</h2>
<p>Unfortunately, it was not all good news. We found only a slight improvement in the sex ratio occurred when temperatures were 3°C above average conditions, even after two generations. This suggests a limitation on the ability of a species to maintain a balanced sex ratio when the water temperature is too high above normal.</p>
<p>We also found that for parents to compensate for the effects of higher temperatures on gender, they must develop from early life at the warm conditions themselves. Parents were not able to adjust the gender of offspring when they only reproduced in warm conditions.</p>
<p>No-one yet knows quite how the Spiny Chromis engineers these amazing adjustments, and it is something we are now investigating. What we do know is that oceans are warming. And transgenerational plasticity has been able to reduce the negative impacts of climate change on offspring gender of a coral reef fish, at least so far.</p>
<p>This represents good news for many species, with negative predictions made from other short-term experiments likely overestimating the true future impacts. However, in many cases the ability for parents to improve their offspring may be limited if warming is too great.</p><img src="https://counter.theconversation.com/content/39053/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jennifer Donelson receives funding from the Ian Potter Foundation. She has previously received funding from ARC Centre of Excellence for Coral Reef Studies and the CSIRO Climate Adaptation Flagship. Jennifer is currently the Hon Treasurer of the Australian Coral Reef Society.</span></em></p>Warmer temperatures can throw off the gender balance in some species. But some fish can adjust their offspring’s gender to compensate, but only if temperatures don’t rise too high.Jennifer Donelson, Chancellor's Postdoctoral Research Fellow, University of Technology SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/364662015-01-22T06:54:12Z2015-01-22T06:54:12ZStrange tale of fish eye evolution shows how new species could be born<figure><img src="https://images.theconversation.com/files/69651/original/image-20150121-29754-rw8ssy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Fish vision just got more complex</span> <span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File:Orange-lined_Triggerfish3.jpg">Janderk</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Evolution allows animals to develop <a href="http://www.popsci.com/science/article/2011-09/ten-new-or-newly-discovered-animal-evolutions-including-humans">superb adaptations</a> to survive and flourish in environmental niches. The evolution of fish eyes is one such intriguing example. However, tracing how different kinds of fish eyes evolved is not always easy. New research is finally throwing some light on this evolutionary feat and it is helping us understand how new species are born.</p>
<p>The diversity of life on Earth is a result of evolutionary processes acting over millions of years. Small changes to the genetic make-up of an organism, such as those that sometimes occur during sexual reproduction, can confer an advantage over competitors and are passed onto the next generation. Changes that result in a disadvantage, by contrast, are filtered out of the population.</p>
<p>While this is most commonly recognised as small mutations, whole-genome, or <a href="http://www.indiana.edu/%7Elynchlab/PDF/Lynch124.pdf">single-gene duplications</a> can also occur and are generally responsible for larger changes. Whole-genome duplications are considered to have laid the genetic foundation on which groups of animals, such as vertebrates and fishes have thrived, while single-gene duplications are thought to facilitate the creation of new species.</p>
<h2>New colours, new perspective</h2>
<p>Opsin (visual) genes are a central component of animal vision and provide fantastic examples of how changes at a molecular level, such as through gene duplication, can affect how animals perceive their environment. This is because molecular changes in opsin genes can result in measurable changes to the colours that an animal can perceive. These changes are important to study because they can help explain how diversity among species is created.</p>
<p>Compared to tetrapods – that is, mammals, amphibians, birds and reptiles – which possess a relatively stable opsin arrangement, gene duplications have helped a vast array of opsin genes to evolve in the bony fishes. In these fishes, the majority of opsin gene duplications are recognised to have occurred in the long-wave (red) and medium-wave (green) genes, with only one previously observed in the short-wave (blue) gene in the spiny-rayed fishes (which include basses and perches). But, when compared to other gene families, the apparent lack of duplications in the blue opsin suggests that its story may be more complex than was appreciated.</p>
<p>With this in mind, Fabio Cortesi, Zuzana Musilová and colleagues set out to re-evaluate the evolutionary history of the blue opsin (SWS2) in bony fishes in a new study published in <a href="http://www.pnas.org/content/early/2014/12/25/1417803112.abstract?sid=430eeb3c-93ed-4855-a33b-bf6356b6ae59">Proceedings of the National Academy of Sciences</a>. </p>
<p>Using the latest gene-sequencing and data-mining techniques, they explored the genomes of close to 100 fish species to examine blue opsin diversity. They found a major gene duplication about 190-170m years ago in a species of fish called neoteleosts. They also found two other gene duplication events: one in the lizardfishes (Aulopiformes), which appears to have been an isolated event, and another that coincided with the emergence of the first percomorph fishes (about 110-130m years ago), which include the dottybacks (Pseudochromidae).</p>
<h2>Through dottybacks’ eyes</h2>
<p>However, just knowing about gene duplication wasn’t enough. Not all changes in genes have an effect on the functions they serve in an animal.</p>
<p>To get an idea of whether this gene duplication conferred a function, they then conducted an in-depth study of the dusky dottyback, <em>Pseudochromis fuscus</em>. They used this species as it was found to possess three duplications of the blue opsin. Using techniques that allow assessment of the spectral sensitivities of an animal’s retina, they found that the dottyback’s retina possessed cone cells that had two sensitivity peaks which fell within the predicted range of the blue opsin duplication. This showed that the duplication did indeed confer a function to detect blue light in their environment, which presumably helps them survive better there.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/69648/original/image-20150121-29743-1tzy2fp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/69648/original/image-20150121-29743-1tzy2fp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/69648/original/image-20150121-29743-1tzy2fp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=370&fit=crop&dpr=1 600w, https://images.theconversation.com/files/69648/original/image-20150121-29743-1tzy2fp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=370&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/69648/original/image-20150121-29743-1tzy2fp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=370&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/69648/original/image-20150121-29743-1tzy2fp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=465&fit=crop&dpr=1 754w, https://images.theconversation.com/files/69648/original/image-20150121-29743-1tzy2fp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=465&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/69648/original/image-20150121-29743-1tzy2fp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=465&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Now we have a better idea of how this dusky dottyback sees the world.</span>
<span class="attribution"><span class="source">Fabio Cortesi</span></span>
</figcaption>
</figure>
<p>But juvenile dottybacks live in the water column while adult dottybacks live on the reef. Perhaps this gene duplication was differently expressed in juvenile and adults? They tested this and found that expression did differ between life stages, suggesting that juvenile and adult dottybacks possess slightly different visual systems from one another.</p>
<p>The changes in genes have a lot to tell us about evolution, but it’s not always possible to understand the story. However, what Cortesi, Musilová and their colleagues have shown is that, with well-planned experiments, we can get enough of a peep into a complex process. We can now say that facilitating the development of new visual sensitivities, gene duplications may allow species to thrive in different light environments which could ultimately result in the evolution of new species.</p><img src="https://counter.theconversation.com/content/36466/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>William Feeney receives funding from an Endeavour Fellowship.</span></em></p>Evolution allows animals to develop superb adaptations to survive and flourish in environmental niches. The evolution of fish eyes is one such intriguing example. However, tracing how different kinds of…William Feeney, Endeavour Research Fellow, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/330222015-01-11T19:27:51Z2015-01-11T19:27:51ZIt’s survival of the most useful when protecting species<figure><img src="https://images.theconversation.com/files/62150/original/26jmqxyh-1413619771.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Coral reefs are like an underwater metropolis -- and function in similar ways.</span> <span class="attribution"><span class="source">Simon Gingins</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Consensus is growing that we are steering towards a <a href="http://www.scientificamerican.com/article/fact-or-fiction-the-sixth-mass-extinction-can-be-stopped/">sixth mass extinction event</a>. There are calls for increased efforts to stop the <a href="http://phys.org/news/2014-10-biodiversity-commits-funding.html">accelerating loss of plants and animals</a>. But do we really need to protect all species from global extinction?</p>
<p>Over the past decade, ecologists have increasingly replaced the value of biodiversity – the diversity of plants, animals and bacteria – with the concept of “functional diversity”. The best way to understand this concept is to compare it with a familiar, striking equivalent: our cities. </p>
<p>Our decision to live in permanent settlements is a success story that is fundamental to the rise of human civilisation. It is based on the partitioning of tasks and professional specialisation, which cohesively provides services to the community.</p>
<p>Food, health, security and construction are among the life-blood of cities. Yet all of these professions are inherently diverse and without this diversity the community would soon collapse.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/64569/original/vj9qmywk-1415949016.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/64569/original/vj9qmywk-1415949016.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/64569/original/vj9qmywk-1415949016.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/64569/original/vj9qmywk-1415949016.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/64569/original/vj9qmywk-1415949016.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/64569/original/vj9qmywk-1415949016.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/64569/original/vj9qmywk-1415949016.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/64569/original/vj9qmywk-1415949016.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>
<figcaption>
<span class="caption">A typical city relies on the diverse services provided by its inhabitants to function.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/stuckincustoms/300928932">Flickr/Trey Ratcliff</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<p>In the natural world, ecosystems such as forests, lakes or deserts are just like cities. Their persistence relies on the functions provided by the organisms living within just as we rely on the grocery store around the corner and our general practitioner.</p>
<h2>The coral city</h2>
<p>In this analogy, exceptionally diverse ecosystems such as coral reefs are the equivalent of bustling metropolitan hubs such as New York, London or Sydney.</p>
<p>With outstanding numbers of organisms comes a plethora of functional roles. Corals build <a href="http://eatlas.org.au/content/relationship-between-corals-and-fishes-great-barrier-reef">structure and living space</a>, selected fishes provide <a href="http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2656.2003.00683.x/abstract">diligent grooming services</a>, big predators control prey populations and some species clean the reef of algae to safeguard coral growth and replenishment.</p>
<p>This latter function, performed predominantly by algae-eating or herbivorous fishes, is important for coral reefs. Herbivorous fishes are like human gardeners, maintaining the beauty and health of reef-building corals. Consequently, great efforts are taken to monitor herbivore communities on coral reefs. </p>
<p>But are these fishes really a homogeneous group of organisms, providing the same service? Absolutely not.</p>
<p>About a decade ago, researchers began to classify herbivorous reef fishes into functional groups based on their feeding behaviours and this is now the go-to characterisation of herbivore communities. </p>
<p>Unfortunately, this rough characterisation appears to be insufficient. Just as gardeners with lawnmowers and landscape artists with hedge clippers perform fundamentally distinct work, herbivorous coral reef fish species differ in their contribution to the reef in more ways than the traditional classification captures.</p>
<p>These distinctions are exemplified, but not exhausted, by:</p>
<ol>
<li>what they eat</li>
<li>how they eat it</li>
<li>where they get it from.</li>
</ol>
<p>The first distinction, what fishes eat, has an obvious impact on targeted prey. A particular alga may be eaten by only a <a href="http://biosciences.gatech.edu/hg/item/191551">single species of fish</a>. If this species declines due to human influence, the algae it typically consumes will thrive and may overpopulate the reef.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/62144/original/xqbbqryq-1413617622.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/62144/original/xqbbqryq-1413617622.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/62144/original/xqbbqryq-1413617622.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=416&fit=crop&dpr=1 600w, https://images.theconversation.com/files/62144/original/xqbbqryq-1413617622.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=416&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/62144/original/xqbbqryq-1413617622.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=416&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/62144/original/xqbbqryq-1413617622.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=523&fit=crop&dpr=1 754w, https://images.theconversation.com/files/62144/original/xqbbqryq-1413617622.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=523&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/62144/original/xqbbqryq-1413617622.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=523&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 unicornfish <em>Naso unicornis</em>.</span>
<span class="attribution"><span class="source">Jordan M Casey</span></span>
</figcaption>
</figure>
<p>Take the unicornfish, <em>Naso unicornis</em> (above), as a typical example. It is often the only consumer of fleshy brown algae and therefore responsible for keeping these algae in check. Unfortunately, this species is also heavily fished in many areas of the world (with the Great Barrier Reef being an exception, at the moment), threatening ecosystems through the loss of its function.</p>
<p>The second characteristic, how herbivores feed, is best explained by the giant humphead parrotfish, <em>Bolbometopon muricatum</em> (below). This species feeds on various species of algae and coral but owing to its extraordinary size and jaw anatomy, it is the only species <a href="http://onlinelibrary.wiley.com/doi/10.1046/j.1461-0248.2003.00432.x/abstract">that significantly erodes reefs</a> through its feeding activity.</p>
<p>In essence, this species creates space for the new settlement of organisms by taking golf-ball-sized bites from the reef. Despite its crucial importance for reef systems through its particular way of foraging, it is heavily exploited in many developing countries.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/62145/original/96z2cg4w-1413618077.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/62145/original/96z2cg4w-1413618077.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/62145/original/96z2cg4w-1413618077.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=427&fit=crop&dpr=1 600w, https://images.theconversation.com/files/62145/original/96z2cg4w-1413618077.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=427&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/62145/original/96z2cg4w-1413618077.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=427&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/62145/original/96z2cg4w-1413618077.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=537&fit=crop&dpr=1 754w, https://images.theconversation.com/files/62145/original/96z2cg4w-1413618077.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=537&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/62145/original/96z2cg4w-1413618077.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=537&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 giant humphead parrotfish, <em>Bolbometopon muricatum</em>.</span>
<span class="attribution"><span class="source">Simon J Brandl</span></span>
</figcaption>
</figure>
<p>The third measure, where herbivores feed, is exemplified by a group of fishes that feed in <a href="http://onlinelibrary.wiley.com/doi/10.1111/1365-2656.12171/abstract">holes and crevices</a> on coral reefs.</p>
<p>While the majority of herbivorous fishes prefer flat, open surfaces, some rabbitfishes (family Siganidae) (below) target concealed surfaces such as crevices to reach for algae.</p>
<p>They may be the only species to control algal growth in these cracks and crevices, a habitat that represents a <a href="http://link.springer.com/article/10.1007/s00338-013-1110-5">refuge for newly settled corals</a>. This difference in their feeding strategy has long been overlooked but may be an important functional process for juvenile corals.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/62147/original/2xsgkmjf-1413618614.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/62147/original/2xsgkmjf-1413618614.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/62147/original/2xsgkmjf-1413618614.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=420&fit=crop&dpr=1 600w, https://images.theconversation.com/files/62147/original/2xsgkmjf-1413618614.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=420&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/62147/original/2xsgkmjf-1413618614.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=420&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/62147/original/2xsgkmjf-1413618614.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=528&fit=crop&dpr=1 754w, https://images.theconversation.com/files/62147/original/2xsgkmjf-1413618614.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=528&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/62147/original/2xsgkmjf-1413618614.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=528&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Some rabbitfishes such as the barred spinefoot, <em>Siganus doliatus</em>, feed on algae in cracks and crevices.</span>
<span class="attribution"><span class="source">Jordan M Casey</span></span>
</figcaption>
</figure>
<p>Given the potential for differentiation outlined by only three cases, it is not hard to imagine that many species will perform <a href="http://www.coralcoe.org.au/news/specialised-species-critical-for-reefs">unique functions on coral reefs</a>.</p>
<p>With this in mind, let us reiterate the questions asked in the beginning. What is the true value of biodiversity? Do we really need all the different critters that populate our world?</p>
<h2>So what can we do?</h2>
<p>The answer is that, at the bare minimum, we need those species that perform unique functions. What’s more is that these species need to be present in large enough numbers at a <em>local</em> scale, which is often inconsistent with <em>global</em> extinction risk.</p>
<p>In other words, the unconscious or conscious local eradication of a single species, which may face no risk of global extinction and is therefore unprotected against local threats, may result in the <a href="http://openscienceworld.com/extinction-risk-not-the-answer-for-reef-futures/">degradation of an entire system</a>. </p>
<p>In this context, humanity has two options. Firstly, we can try to play it safe and strive to protect all species, globally and locally, to diminish our risk of accidentally removing important ecosystem components. While this will ensure that any crucial ecosystem function is adequately covered, this is costly and rather unrealistic.</p>
<p>Secondly, we can take our chances and strive to identify and protect only important ecological functions and their main performers, which are the most crucial pieces in the complex puzzle that is our natural world. This will require increasing research efforts to investigate the tight links between biodiversity and ecosystem function, but has the potential to overlook cryptically important functions.</p>
<p>The dramatic consequences of such oversight are visible in the collapse of some ecosystems such as <a href="http://www.bbc.com/news/science-environment-28113331">Caribbean coral reefs</a>, where the exploitation of herbivorous fishes and the loss of sea-urchins has triggered shifts from coral-dominated systems to algal beds. </p>
<p>Unfortunately, globally, we commonly fail to fulfil either of these options by affecting entire ecosystems through large-scale developments.</p>
<h2>Collateral damage</h2>
<p>In Australia, for example, although herbivorous fishes are rarely targeted by fishermen and are in no threat of global extinction, we continue to collaterally impact the Great Barrier Reef through activities such as <a href="https://theconversation.com/mounting-evidence-shows-dredge-spoil-threat-to-the-great-barrier-reef-29773">dredging</a> or the extraction of large predators such as sharks and groupers, not knowing about the potential consequences for organisms inhabiting the reef or the functions they perform.</p>
<p>Do we really want to jeopardise the future of the natural coral cities that our planet has to offer? And would we equally lightheartedly risk the degradation of our great cultural centres such as New York, Paris, London or Sydney? I don’t think so.</p>
<p>So there is a clear need to increase our research efforts regarding the role of functional diversity on coral reefs and in other ecosystems around the world in order to identify those critical processes that we must not disturb.</p>
<p>Without this knowledge, our actions and interferences with the natural world are little more than a blind stumble through a minefield of most dire and irreversible consequences.</p><img src="https://counter.theconversation.com/content/33022/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Simon J. Brandl receives funding from the Australian Research Council Centre of Excellence for Coral Reef Studies.</span></em></p>Consensus is growing that we are steering towards a sixth mass extinction event. There are calls for increased efforts to stop the accelerating loss of plants and animals. But do we really need to protect…Simon J. Brandl, PhD-Candidate in Coral Reef Ecology, James Cook UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/229082014-03-05T19:22:30Z2014-03-05T19:22:30ZOceans in motion: why some fish can’t go with the flow<figure><img src="https://images.theconversation.com/files/42774/original/zwh7m2mq-1393633148.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Changing waves and currents can keep fish on the move.</span> <span class="attribution"><span class="source">Jordan Casey</span></span></figcaption></figure><p>Have you ever been snorkelling or scuba diving on a windy day when there are lots of waves? Did you notice how much that flow of water against your body affected your ability to swim and control your movements underwater? Well, fish feel the same way!</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/c7mN4xtUssQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Water flow on a wave-exposed coral reef.</span></figcaption>
</figure>
<p>Water flow, in waves and currents, plays a huge role in determining whether fish can survive in freshwater or marine habitats. Some species, such as tuna or salmon, are designed for high speed swimming, and thrive in fast flowing water.</p>
<p>Others, such as pufferfish, are not so well equipped to handle the challenges of living in high flow environments, and prefer the peace and calm of sheltered lagoons.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/42714/original/xryrg445-1393552990.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/42714/original/xryrg445-1393552990.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/42714/original/xryrg445-1393552990.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/42714/original/xryrg445-1393552990.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/42714/original/xryrg445-1393552990.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/42714/original/xryrg445-1393552990.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/42714/original/xryrg445-1393552990.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/42714/original/xryrg445-1393552990.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">Stay calm.</span>
<span class="attribution"><a class="source" href="http://www.flickr.com/photos/motelface/3846613872/sizes/l/">Flickr/ Motelface</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>But even good swimmers have their limits. For example, high rates of water discharge from hydroelectric dams can hinder the upstream movements of fish – think of North American salmon or Macquarie perch in Australia.</p>
<p>Not all individual fish are affected the same, of course. Bigger, stronger adults are generally more capable of fighting against strong currents, but smaller, younger fish will be less likely to make it. This has obvious consequences for the age structure and survival of fish populations in the long run.</p>
<h2>Waves, coastlines and coral reefs</h2>
<p>On the Australian coastline, waves created by winds are a major physical force that fish have to contend with.</p>
<p>Some fish species are “rovers” without a fixed home range, and constantly swim over large areas in search of food or mates. Examples include species of surgeonfish and parrotfish. Since they do not need to defend a territory, these fish can take advantage of waves to help them move around, much like surfers do.</p>
<p>In contrast, many other species, such as damselfish, have small territories that they defend vigorously against unwelcome intruders to protect their food and other resources. To do this, they constantly have to swim against the water flow to avoid being swept away.</p>
<p>Colleagues and I have found that fish <a href="http://jeb.biologists.org/content/217/3/414.abstract?sid=2a5c25e2-5e92-477a-8a77-d071fa8d79d7">spend a lot more energy</a> when they have to swim against big waves compared to a regular, steady current at the same average speed. This makes sense: humans also burn a lot more energy during interval training (when constantly changing between a sprint and a jog) compared to running at a constant speed.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/IuboHhqIMY0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Shiner surfperch in swim tunnel.</span></figcaption>
</figure>
<p>Many fish species regularly face these challenges, especially on Australia’s Great Barrier Reef.</p>
<p>Coral reefs are shallow habitats because corals need light to photosynthesise and produce their food. Because of their proximity to the surface, coral reefs are often very wavy habitats. This poses a real challenge for the estimated 25% of marine species found on coral reefs, 4,000 of which are fish.</p>
<h2>Climate change</h2>
<p>Researchers are increasingly concerned that accelerating changes in weather patterns are affecting fish and other aquatic organisms. Rivers, lakes and coastal habitats are ecologically, socially and economically important places, so it’s worth investing the time to research the impacts of climate change on these areas.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/42390/original/zkrdxj66-1393278008.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/42390/original/zkrdxj66-1393278008.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/42390/original/zkrdxj66-1393278008.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=432&fit=crop&dpr=1 600w, https://images.theconversation.com/files/42390/original/zkrdxj66-1393278008.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=432&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/42390/original/zkrdxj66-1393278008.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=432&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/42390/original/zkrdxj66-1393278008.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=543&fit=crop&dpr=1 754w, https://images.theconversation.com/files/42390/original/zkrdxj66-1393278008.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=543&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/42390/original/zkrdxj66-1393278008.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">How disturbances from waves affect the movements of predators and prey likely depends on their relative size.</span>
<span class="attribution"><span class="source">Jordan Casey</span></span>
</figcaption>
</figure>
<p>In addition to <a href="https://theconversation.com/fish-may-end-up-in-hot-water-as-climate-warms-the-ocean-22980">warming temperatures</a> and <a href="https://theconversation.com/global-warmings-evil-twin-ocean-acidification-19017">acidified oceans</a>, sea surface levels, and thus tidal amplitudes, are also predicted to rise as a consequence of climate change.</p>
<p>Already, these trends in weather are being <a href="http://onlinelibrary.wiley.com/doi/10.1002/2013GL058777/abstract">documented</a>. Storms are also increasing in frequency and intensity in ocean basins around the globe, according to the chapter on Ocean Change in the International Panel on Climate Change’s <a href="https://www.ipcc.ch/report/ar5/wg1/">report last year</a>. With higher winds and larger tides come bigger waves.</p>
<p>Waves, tides and currents are an everyday part of life for fish living in fast-flowing waters, but new extremes in wind speed and wave height may push some species over the edge.</p>
<h2>What can fish do?</h2>
<p>If waves are costly for some fish, then why don’t they move to calmer locations? Fish can swim, after all. And some won’t even have to swim very far to reach calmer waters. Water velocity can vary across very small scales on coral reefs.</p>
<p>A new underwater instrument was developed at James Cook University to measure wave forces on the sea floor.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/42388/original/6kykscbs-1393276575.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/42388/original/6kykscbs-1393276575.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/42388/original/6kykscbs-1393276575.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=808&fit=crop&dpr=1 600w, https://images.theconversation.com/files/42388/original/6kykscbs-1393276575.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=808&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/42388/original/6kykscbs-1393276575.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=808&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/42388/original/6kykscbs-1393276575.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1016&fit=crop&dpr=1 754w, https://images.theconversation.com/files/42388/original/6kykscbs-1393276575.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1016&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/42388/original/6kykscbs-1393276575.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1016&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 instrument on a sheltered reef location with the guide rod construction and drag-sphere placement.</span>
<span class="attribution"><a class="source" href="http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0083240">Jacob L. Johansen</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p><a href="http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0083240#pone-0083240-g005">A study</a> from January this year using this device showed that water speeds decrease dramatically the deeper you go on coral reefs at Lizard Island. On a windy day, the water flow speed at 9m below the surface is about one quarter of the flow speed at 3m depth.</p>
<p>But there are many reasons why fish might not move to calmer reefs or go deeper to avoid waves:</p>
<ul>
<li>sunlight is reduced with increasing water depth, so the shallowest, and waviest, part of the reef, where corals receive the most sunlight, is also the most productive and best habitat for fish</li>
<li>waves near the surface mix the water and carry the nutrients and plankton that feed fish</li>
<li>good places to live are at premium on coral reefs and species are all vying for space. This means that fish wanting to move will have to compete with already established residents and dislodge them if they want to take over their homes.</li>
</ul>
<h2>What can we do?</h2>
<p>Our understanding of how fish deal with waves, let alone adapt to changes in their flow environment, is very limited.</p>
<p>Answers to many important questions remain elusive – what aspects of their shape, physiology and behaviour allow certain species to thrive in their current habitats?</p>
<p>How do waves affect important phenomena like the outcome of predator-prey encounters, competition between individuals, or the survival of small, larval fish on the reef?</p>
<p>How does water flow interact with other stressors like temperature changes, ocean acidification and fishing pressure in shaping our changing marine communities?</p>
<p>Ultimately, more research into these questions will help us understand how fish might respond to expected changes in their flow environment. These answers will be critical to inform marine resource managers and help them identify and target species that are especially sensitive to increases in wave intensity.</p><img src="https://counter.theconversation.com/content/22908/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dominique Roche receives funding from the Australian Research Council Centre of Excellence for Coral Reef Studies.</span></em></p>Have you ever been snorkelling or scuba diving on a windy day when there are lots of waves? Did you notice how much that flow of water against your body affected your ability to swim and control your movements…Dominique Roche, Postdoctoral Fellow, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/123122013-02-21T03:19:01Z2013-02-21T03:19:01ZDazzling or deceptive? The markings of coral reef fish<figure><img src="https://images.theconversation.com/files/20466/original/bzsp643h-1361339912.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">How and why have the colour patterns of coral reef fish changed over time?</span> <span class="attribution"><span class="source">David Cook</span></span></figcaption></figure><p>Have you ever wondered why coral reef fishes are so brilliantly coloured and bizarrely patterned? A quick flick through any coral reef fish guide will leave you bewildered and awed.</p>
<p>To answer this question, we need to think about what animals, in general, use their colour patterns for. There is, in fact, a range of uses: for instance, many must have patterns that are both eye-catching to would-be mates but also appear cryptic to lurking predators. </p>
<p>My colleagues, <a href="http://www.manchester.ac.uk/research/john.fitzpatrick/personaldetails">Dr John Fitzpatrick</a> at University of Manchester, UK, <a href="http://web.abo.fi/fak/mnf/biol/eco/beeg/sami.html">Dr Sami Merilaita</a> at Abo Akademi University, Finland, and I, recently used a “comparative approach” to try to unravel the mystery behind the evolution of spots and stripes in <a href="http://animals.nationalgeographic.com.au/animals/fish/butterflyfish/">butterflyfishes</a> in our original research, <a href="http://rspb.royalsocietypublishing.org/content/280/1757/20122730.short?rss=1">published today</a> in Proceedings of the Royal Society B. </p>
<p>We tested a number of predictions about how these markings should evolve if they help butterflyfishes avoid being eaten.</p>
<p>So, what significant questions were we able to answer?</p>
<h2>Can your colour patterns help you avoid being eaten?</h2>
<p>Camouflage is a well-known way for prey to avoid being eaten, but it is not the only tactic. Striking markings such as spots and stripes can deceive or dazzle predators to foil attempted attacks.</p>
<p>Markings such as spots and eyespots (circles with a ring around the outside) are a particular source of intrigue for biologists and are common in a number of animals, including coral reef fishes. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/20467/original/vcztbc24-1361397020.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/20467/original/vcztbc24-1361397020.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=474&fit=crop&dpr=1 600w, https://images.theconversation.com/files/20467/original/vcztbc24-1361397020.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=474&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/20467/original/vcztbc24-1361397020.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=474&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/20467/original/vcztbc24-1361397020.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=596&fit=crop&dpr=1 754w, https://images.theconversation.com/files/20467/original/vcztbc24-1361397020.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=596&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/20467/original/vcztbc24-1361397020.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=596&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Painting of a hypothetical butterflyfish.</span>
<span class="attribution"><span class="source">Shaun Collin</span></span>
</figcaption>
</figure>
<p>The idea that spots and eyespots might help prey to avoid being eaten by predators has been around for some time. Eyespots might intimidate or scare predators by mimicking the eyes of the predators’ enemies. </p>
<p>Another idea is that they deceive predators by giving the impression of a head at the wrong end of the body. While some of these ideas have gained support from studies of butterflies and moths, the role of these markings in fishes has remained a mystery.</p>
<h2>Why have spots and stripes evolved?</h2>
<p>One exciting way to tackle these sorts of evolutionary questions is to use a comparative approach – as we did – which allows you to link a species’ colour patterns with its ecology, while taking into account shared ancestry (because closely related species are more likely to resemble one another). </p>
<p>We obtained phylogentic data (showing the evolutionary relationships among species) on the butterflyfish family from <a href="http://www.ncbi.nlm.nih.gov/pubmed/20487131">original research</a> published by <a href="http://www.jcu.edu.au/mtb/staff/az/JCUDEV_014222.html">Professor David Bellwood</a> and colleagues at James Cook University. We then collected data on the colour patterns and ecology of each species by examining fish guide books, orginal research papers and online resources.</p>
<p>To our surprise, we found little support for the idea that spots provide protection from predators. But we noticed that fish with spots and eyespots always had eye stripes. These markings obscure the eye, perhaps diverting attention away from the eye and towards the spot or eyespot.</p>
<h2>Have stripes evolved for multiple purposes?</h2>
<p>When we looked at the evolution of striped patterns, we found species that were often found in shoals had fewer stripes.</p>
<p>Perhaps shoaling species tend to inhabit open water where their lack of patterning allows them to be camouflaged against the plain background. We also found that butterflyfish with broad diets tended to have more stripes. </p>
<p>If stripes work to break up the fish’s body outline, maybe these markings allow fish to expand their feeding activity to a greater number of habitats. There are many possible explanations for our findings, not all of which are related to predator defence.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/20468/original/hvqrwzgk-1361397509.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/20468/original/hvqrwzgk-1361397509.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/20468/original/hvqrwzgk-1361397509.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/20468/original/hvqrwzgk-1361397509.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/20468/original/hvqrwzgk-1361397509.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/20468/original/hvqrwzgk-1361397509.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/20468/original/hvqrwzgk-1361397509.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Saddle butterflyfish as seen in Taiwan.</span>
<span class="attribution"><span class="source">Vincent Chen</span></span>
</figcaption>
</figure>
<h2>Beauty is in the eye of the beholder</h2>
<p>One of the most important things to remember when studying the patterns and colours of animals is that animals have very different visual systems to humans. In fact, many fish may have a system of colour vision that is far more complex than our own. </p>
<p>An <a href="http://rstb.royalsocietypublishing.org/content/355/1401/1257.abstract">influential paper</a> published in 2000 by <a href="http://www.uq.edu.au/sbms/staff/professor-justin-marshall">Professor Justin Marshall</a> at The University of Queensland illustrates this key point. Professor Marshall showed patterns that appear bright and bold to us might actually appear rather drab to fish, particularly if they are viewed from a distance. </p>
<p>One future challenge is to figure out how patterns such as spots and stripes appear when viewed through the eyes of the fish. Only then can we start to understand and explain the astonishing diversity of reef fish colour patterns. </p><img src="https://counter.theconversation.com/content/12312/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jennifer Kelley 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>Have you ever wondered why coral reef fishes are so brilliantly coloured and bizarrely patterned? A quick flick through any coral reef fish guide will leave you bewildered and awed. To answer this question…Jennifer Kelley, Postdoctoral Research Fellow, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/46102011-12-14T03:39:40Z2011-12-14T03:39:40ZThe oceans are getting warmer, but tropical reef fish could acclimate<figure><img src="https://images.theconversation.com/files/6194/original/kj52zx4n-1323218328.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">It takes just two generations to adapt to warmer ocean temperatures.</span> <span class="attribution"><span class="source">Jennifer Donelson</span></span></figcaption></figure><p>The average temperature of the oceans has already increased significantly due to global warming and will continue to warm rapidly in coming decades. If we are going to effectively manage and conserve fish populations, we need to understand if (and how) these species will adjust to higher temperatures. </p>
<p>Unfortunately, our current understanding of how species might acclimate and adjust to rising temperatures is incomplete. <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1323.html">A recent study</a> completed by my colleagues and I will hopefully develop our understanding in this area.</p>
<p>Tropical species are <a href="http://faculty.washington.edu/tewksjj/articles/Tewksbury%20et%20al%20Science%202008.pdf">expected to be among the groups most sensitive</a> to environmental warming because they have <a href="http://faculty.washington.edu/tewksjj/articles/deutsch%20et%20al%202008.pdf">evolved in a relatively stable thermal environment</a>. In addition, “ectothermic” (cold-blooded) organisms – such as fish and lizards – are likely to be strongly impacted by rises in temperature since their body temperature varies directly with the environmental temperature.</p>
<p>Generally, we expect some capacity for <a href="http://www.biolsci.monash.edu.au/staff/fellows/sgro/docs/hoffmann-sgro-2011.pdf">acclimation and adaptation</a> since we already know this occurs between populations. Differences in performance (the ability to function within the environment) can be observed between <a href="http://jeb.biologists.org/content/204/24/4227.short">the same species living at different latitudes</a> and therefore different temperature regimes.</p>
<p>But there is limited knowledge of whether species’ evolutionary response to climate change will occur quickly enough to keep <em>up</em> with climate change. One way to approach this question is by running long-term experiments that simulate future conditions (as we did).</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/6195/original/rwtmbx8k-1323218469.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/6195/original/rwtmbx8k-1323218469.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/6195/original/rwtmbx8k-1323218469.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/6195/original/rwtmbx8k-1323218469.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/6195/original/rwtmbx8k-1323218469.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/6195/original/rwtmbx8k-1323218469.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/6195/original/rwtmbx8k-1323218469.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&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"><span class="source">Jennifer Donelson</span></span>
</figcaption>
</figure>
<p>For fish and other aquatic animals, the ability to perform <a href="http://en.wikipedia.org/wiki/Aerobic_exercise">aerobic activity</a> at various temperatures <a href="http://www.sciencemag.org/content/315/5808/95">relates to their growth and abundance</a>. When aerobic capacity drops too much, the animal can no longer effectively perform activities such as feeding and avoiding predators.</p>
<p>Myself and my colleagues investigated this phenomenon in current-day populations of one particular coral reef fish species (<em>Acanthochromis polyacanthus</em>). We found that water temperature increases of +1.5°C and +3.0°C caused large reductions in aerobic capacity, which would affect the fish’s ability to persist in a warmer, future environment. We also found that when fish were grown for two generations at 1.5°C and 3.0°C greater than current-day averages, aerobic capacity no longer declined and was equal to that of the current-day population. </p>
<p>In other words, we found that over two generations, tropical reef fish can acclimate to the warmer water temperatures we could see as a result of global warming.</p>
<p>But there are likely to be penalties for fish that successfully adjust to higher temperatures. Our observations suggest the acclimatised offspring are smaller on average than their parents and might not be able to reproduce at the same rate as their predecessors. We also don’t know whether this rapid ability to cope with increased temperatures is common among coral reef fish species.</p>
<p>Our study reveals that transgenerational acclimation is a potentially important mechanism for coping with rapid climate change. Such acclimation may allow some fish populations to persist across their current <a href="http://en.wikipedia.org/wiki/Range_(biology)">range</a>, instead of having to move in search of cooler waters.</p><img src="https://counter.theconversation.com/content/4610/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jennifer Donelson receives funding from ARC Centre of Excellence for Coral Reef Studies, CSIRO Climate Adaptation Flagship, the Australian Coral
Reef Society and the GBRMPA Science for Management Awards.</span></em></p>The average temperature of the oceans has already increased significantly due to global warming and will continue to warm rapidly in coming decades. If we are going to effectively manage and conserve fish…Jennifer Donelson, PhD Candidate, School of Marine and Tropical Biology, James Cook UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/44742011-11-25T22:13:39Z2011-11-25T22:13:39ZDoes the Coral Sea marine park proposal provide enough protection?<figure><img src="https://images.theconversation.com/files/5898/original/babasteve-jpg-1322225205.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Coral Sea could soon become the world's largest marine park.</span> <span class="attribution"><span class="source">babasteve</span></span></figcaption></figure><p>The release of the <a href="http://www.environment.gov.au/coasts/mbp/coralsea/consultation/index.html">Coral Sea Commonwealth marine reserve proposal</a> is a milestone achievement in marine protection.</p>
<p>The area proposed to be covered is larger than that of many small European nations. In fact, if it comes to fruition, it will be one of the largest marine parks on the planet.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/5897/original/coral-sea-islands-gif-1322224964.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/5897/original/coral-sea-islands-gif-1322224964.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=645&fit=crop&dpr=1 600w, https://images.theconversation.com/files/5897/original/coral-sea-islands-gif-1322224964.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=645&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/5897/original/coral-sea-islands-gif-1322224964.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=645&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/5897/original/coral-sea-islands-gif-1322224964.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=811&fit=crop&dpr=1 754w, https://images.theconversation.com/files/5897/original/coral-sea-islands-gif-1322224964.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=811&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/5897/original/coral-sea-islands-gif-1322224964.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=811&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p>But there is a caveat here: more than half of the marine reserve is not afforded full protection, with recreational fishing and some forms of commercial fishing to continue unabated. This is clearly a compromise to appease the recreational fishing lobby and to maintain some commercial fisheries.</p>
<p>It is <a href="http://www.fao.org/fishery/topic/12273/en">well supported scientifically</a> that fisheries extraction is a major threat to world fish populations. The selective removal of top predators — such as sharks, gropers and mackerels — may also indirectly affect whole ecosystems, so fishing needs to be managed closely.</p>
<p>In addition, while it is commendable that the fully protected “Marine National Park Zone” spans a huge range of latitudes, it has been relegated to the easternmost side of the reserve.</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/5896/original/imagebloomfield-lodge-colyn-huber-jpg-1322224705.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/5896/original/imagebloomfield-lodge-colyn-huber-jpg-1322224705.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=980&fit=crop&dpr=1 600w, https://images.theconversation.com/files/5896/original/imagebloomfield-lodge-colyn-huber-jpg-1322224705.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=980&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/5896/original/imagebloomfield-lodge-colyn-huber-jpg-1322224705.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=980&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/5896/original/imagebloomfield-lodge-colyn-huber-jpg-1322224705.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1232&fit=crop&dpr=1 754w, https://images.theconversation.com/files/5896/original/imagebloomfield-lodge-colyn-huber-jpg-1322224705.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1232&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/5896/original/imagebloomfield-lodge-colyn-huber-jpg-1322224705.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1232&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The proposal has balanced conservation needs with those of the fishing industry.</span>
<span class="attribution"><span class="source">Bloomfield Lodge/Colyn Huber</span></span>
</figcaption>
</figure>
<p>This means a huge swag of ocean adjacent to the World Heritage listed <a href="http://www.gbrmpa.gov.au/zoning-permits-and-plans/zoning/zoning-maps">Great Barrier Reef Marine Park</a>, and ocean containing critical spawning sites for black marlin, is poorly protected from key extractive threats. </p>
<p>Many marine organisms travel through zones and these “pathways of connectivity” mean the zoning of one region can affect the conservation performance of adjacent zones, even if the latter zone is fully protected.</p>
<p>In 2009 I travelled to the <a href="http://en.wikipedia.org/wiki/Wreck_Reefs">Wreck Reefs</a> in the southern section of the proposed new Coral Sea Marine Reserve. Under the proposal, this entire region would be a “multiple use zone” allowing many forms of recreational and commercial fishing.</p>
<p>I found Wreck Reefs to be in excellent condition — a pristine paradise of corals and associated fishes and invertebrates. In addition, the <a href="http://en.wikipedia.org/wiki/Cay">cays</a> (sandy islands) supported abundant seabirds, and are of historical significance.</p>
<p>(At the start of the 19th century, <a href="http://anmm.wordpress.com/2009/12/04/wreck-reefs-expedition-history-of-the-area/">several vessels from Matthew Flinders’ fleet</a> were <a href="http://nla.gov.au/nla.pic-an4910322">wrecked</a> at Porpoise Reefs. <a href="http://www.sims.org.au/wp-content/uploads/2011/08/Newsletter-2010-02-23-page-1-62.pdf">Remnants of these vessels still exist today</a>.)</p>
<p><a href="http://environment.gov.au/coasts/mbp/coralsea/consultation/pubs/coralsea-map.pdf"><figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/5894/original/map-jpg-1322224014.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/5894/original/map-jpg-1322224014.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=423&fit=crop&dpr=1 600w, https://images.theconversation.com/files/5894/original/map-jpg-1322224014.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=423&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/5894/original/map-jpg-1322224014.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=423&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/5894/original/map-jpg-1322224014.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=531&fit=crop&dpr=1 754w, https://images.theconversation.com/files/5894/original/map-jpg-1322224014.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=531&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/5894/original/map-jpg-1322224014.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=531&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The proposed Commonwealth marine reserve (click for larger image)</span>
<span class="attribution"><span class="source">Commonwealth of Australia</span></span>
</figcaption>
</figure></a></p>
<p>While fish life at the Wreck Reefs was plentiful at the time of my visit, populations of reef predators — such as gropers, snappers and mackerels — seemed depleted. I noted at the time that:</p>
<p>“It is likely that fishing pressure (charters mainly), coupled with isolation (reducing connectivity with other fish populations, and so lowering replenishment potential) are to blame, which is a sobering reminder that human influence extends into apparently pristine locations”.</p>
<p>The Commonwealth <a href="http://www.environment.gov.au/coasts/mbp/coralsea/publications/pubs/coralsea-reserve-proposal.pdf">consultation paper</a> suggests the Wreck reefs are “shallow reef systems” that are “remote and relatively pristine”. I would argue these reefs may already have been negatively affected by human exploitation.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/5895/original/peter-nijenhuis-jpg-1322224345.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/5895/original/peter-nijenhuis-jpg-1322224345.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/5895/original/peter-nijenhuis-jpg-1322224345.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/5895/original/peter-nijenhuis-jpg-1322224345.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/5895/original/peter-nijenhuis-jpg-1322224345.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1130&fit=crop&dpr=1 754w, https://images.theconversation.com/files/5895/original/peter-nijenhuis-jpg-1322224345.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1130&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/5895/original/peter-nijenhuis-jpg-1322224345.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1130&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Coral Sea marine park proposal could do more to protect marine environments.</span>
<span class="attribution"><span class="source">Peter Nijenuis</span></span>
</figcaption>
</figure>
<p>Such isolated reefs probably have reduced linkages to sources of larvae on the Great Barrier Reef, and might therefore be more vulnerable to human interference and likely to recover more slowly.</p>
<p>Therefore, while I consider the Coral Sea Commonwealth marine reserve proposal to be a great step forward in marine biodiversity conservation, I would have preferred a higher level of protection in western and southern regions.</p>
<p>Rigorous monitoring of the performance of the new reserve will also be critical in evaluating its effectiveness. This won’t be a cheap exercise, given the isolation of the region, and at this stage, it’s unclear what resources and committment will be allocated to this task.</p>
<p><em>The Commonwealth marine reserve proposal for the Coral Sea has been released for public consultation. For more information about the proposal, visit the <a href="http://environment.gov.au/coasts/mbp/coralsea/index.html">Department of Sustainability, Environment, Water, Population and Communities website</a>.</em></p>
<p><strong>Further reading:</strong></p>
<ul>
<li><a href="http://theconversation.com/commonwealth-proposes-coral-sea-marine-reserve-4471">Commonwealth proposes Coral Sea marine reserve</a></li>
</ul><img src="https://counter.theconversation.com/content/4474/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Booth 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 release of the Coral Sea Commonwealth marine reserve proposal is a milestone achievement in marine protection. The area proposed to be covered is larger than that of many small European nations. In…David Booth, Professor of Marine Ecology, University of Technology SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/35912011-09-29T20:31:55Z2011-09-29T20:31:55ZPoverty, not population, is ruining coral reef ecosystems<figure><img src="https://images.theconversation.com/files/3896/original/fishing_PNG_Fran_Tapia.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Protecting coral reefs means thinking about people, not just marine species.</span> <span class="attribution"><span class="source">Fran Tapia</span></span></figcaption></figure><p>Overfishing is a serious problem on many of the world’s coral reefs – a problem that is generally attributed to too many people. But <a href="http://www.sciencedirect.com/science/article/pii/S0960982208015728">our research</a> has found that economic development, rather than population, is the main driver of overfishing on coral reefs in the western Indian Ocean. </p>
<p>Interestingly, the heaviest overfishing on coral reefs occurs in countries part way up the development ladder. Countries with either very low or high levels of development tend to have reef fisheries in pretty good shape – about four times the reef fish biomass of the intermediate development sites.</p>
<p>Maybe the easiest way to explain our results is for you to imagine a valley, with steep mountains on either side. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/3895/original/fishing_madagascar_Benoit_Balanca.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/3895/original/fishing_madagascar_Benoit_Balanca.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/3895/original/fishing_madagascar_Benoit_Balanca.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/3895/original/fishing_madagascar_Benoit_Balanca.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/3895/original/fishing_madagascar_Benoit_Balanca.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/3895/original/fishing_madagascar_Benoit_Balanca.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/3895/original/fishing_madagascar_Benoit_Balanca.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">
<figcaption>
<span class="caption">Madagascan taboos help protect fish.</span>
<span class="attribution"><span class="source">Benoit Balanca</span></span>
</figcaption>
</figure>
<p>On top of the mountain at one side of the valley are the least developed places such as Madagascar. Here, fishing technology is pretty basic, which means it is harder to plunder the reefs. </p>
<p>Village traditions also limit fishing. For example, in parts of Madagascar there are taboos on the days people can fish, the types of fish they can eat, the gear they use, and even sacred areas where nobody is allowed to fish. </p>
<p>I’ve studied these types of taboos from Papua New Guinea across the Indian Ocean to Madagascar. Where they operate there is 25-300% higher fish biomass. In some places the coral cover is twice as high, too. </p>
<p>However, these systems only seem to operate in areas with low levels of development, low populations (in Papua New Guinea the threshold seems to be about 1,000 people), and far from markets (about 16 kilometres).</p>
<p>On the mountain on the other side of the valley are countries such as Seychelles. They have a higher economic diversity and a lower reliance on reef fish for food or profit. </p>
<p>Here scientific and management institutions help to effectively govern reef fisheries, which are in relatively good condition.</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/3898/original/fishing_seychelles_whl_travel.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/3898/original/fishing_seychelles_whl_travel.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=391&fit=crop&dpr=1 600w, https://images.theconversation.com/files/3898/original/fishing_seychelles_whl_travel.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=391&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/3898/original/fishing_seychelles_whl_travel.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=391&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/3898/original/fishing_seychelles_whl_travel.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=491&fit=crop&dpr=1 754w, https://images.theconversation.com/files/3898/original/fishing_seychelles_whl_travel.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=491&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/3898/original/fishing_seychelles_whl_travel.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=491&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In the Seychelles, regulation has kept fish stocks at comparatively healthy levels.</span>
<span class="attribution"><span class="source">whl.travel</span></span>
</figcaption>
</figure>
<p>Now if you take a few steps from either mountain, you’ll quickly find yourself sliding down the slopes to the bottom of the valley. </p>
<p>Here, societies are moderately developed, which means they have the technology to plunder their reefs, but don’t have the institutions to effectively manage them. The traditional systems have broken down, but national governments are often too inadequately resourced to effectively manage fisheries without the full support of local communities.</p>
<p>In this valley of depletion, the amount of fish is only about a quarter of the more-or-less developed places. </p>
<p>Because of declining catches, many fishermen here have to fish harder and harder just to survive and some are caught in a “poverty trap”. This occurs when that short-term need to survive outweighs any long-term advantages
to conservation or sustainable management. </p>
<p>In this situation, some fishers resort to using highly destructive gear such as <a href="http://www.fao.org/fishery/geartype/102/en">seine nets</a> or explosives to make ends meet. This, of course, damages the fishery further and can lead to a cycle of poverty and reef destruction.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/3897/original/fishing_PNG_dmscvan.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/3897/original/fishing_PNG_dmscvan.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/3897/original/fishing_PNG_dmscvan.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/3897/original/fishing_PNG_dmscvan.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/3897/original/fishing_PNG_dmscvan.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/3897/original/fishing_PNG_dmscvan.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/3897/original/fishing_PNG_dmscvan.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">Community customs, like those in PNG, keep a lid on overfishing.</span>
<span class="attribution"><span class="source">dmscvan</span></span>
</figcaption>
</figure>
<p>The real danger here is that if plundered too hard, these coral reefs may lose their resilience and not come back when and if economic conditions improve.</p>
<p>So there is both a good and bad side to the story. </p>
<p>The bad news is that the valley of depletion is very wide and sliding into it is much easier than climbing out. </p>
<p>Whether the world has coral reefs in the future will not only depend on whether we tackle climate change challenges such as ocean acidification and coral bleaching. It will also largely depend on whether developing countries can navigate the transition from deep poverty to prosperity without ruining their fisheries. </p>
<p>For societies already in a poverty trap, governments and donors need to get them out and couple this development with good governance and strong institutions.</p>
<p>The good news is that the path to reef destruction is not inevitable. Coral reefs can be sustained with the right combination of approaches, which includes fishery closures, property rights, and gear restrictions while at the same time tackling poverty as a root cause of reef decline.</p>
<p><em>This article was originally published in <a href="http://issuu.com/wiomsa">People & The Environment</a>.</em></p><img src="https://counter.theconversation.com/content/3591/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joshua Cinner receives funding from ARC, WIOMSA, National Geographic, MacArthur Foundation. </span></em></p>Overfishing is a serious problem on many of the world’s coral reefs – a problem that is generally attributed to too many people. But our research has found that economic development, rather than population…Joshua Cinner, Senior Research Fellow, ARC Centre of Excellence, Coral Reef Studies, James Cook UniversityLicensed as Creative Commons – attribution, no derivatives.