We’ve just discovered two new shark species – but they may already be threatened by fishing



One of the newly discovered sixgilled sawshark species (Pliotrema kajae).
Simon Weigmann, Author provided

Per Berggren, Newcastle University and Andrew Temple, Newcastle University

Finding a species that’s entirely new to science is always exciting, and so we were delighted to be a part of the discovery of two new sixgill sawsharks (called Pliotrema kajae and Pliotrema annae) off the coast of East Africa.

We know very little about sawsharks. Until now, only one sixgill species (Pliotrema warreni) was recognised. But we know sawsharks are carnivores, living on a diet of fish, crustaceans and squid. They use their serrated snouts to kill their prey and, with quick side-to-side slashes, break them up into bite-sized chunks.

The serrated snout of a sixgill sawshark (Pliotrema annae).
Ellen Barrowclift-Mahon/Marine MEGAfauna Lab/Newcastle University., Author provided

Sawsharks look similar to sawfish (which are actually rays), but they are much smaller. Sawsharks grow to around 1.5 metres in length, compared to 7 metres for a sawfish and they also have barbels (fish “whiskers”), which sawfish lack. Sawsharks have gills on the side of their heads, whereas sawfish have them on the underside of their bodies.

A sixgill sawshark (Pliotrema annae) turned on its side, showing gills and barbels.
Ellen Barrowclift-Mahon, Author provided

Together with our colleagues, we discovered these two new sawsharks while researching small-scale fisheries that were operating off the coasts of Madagascar and Zanzibar. While the discovery of these extraordinary and interesting sharks is a wonder in itself, it also highlights how much is still unknown about biodiversity in coastal waters around the world, and how vulnerable it may be to poorly monitored and managed fisheries.

The three known species of sixgill sawshark. The two new species flank the original known species. From left to right: Pliotrema kajae, Pliotrema warreni (juvenile female) and Pliotrema annae (presumed adult female).
Simon Weigmann, Author provided

Fishing in the dark

Despite what their name might suggest, small-scale fisheries employ around 95% of the world’s fishers and are an incredibly important source of food and money, particularly in tropical developing countries. These fisheries usually operate close to the coast in some of the world’s most important biodiversity hotspots, such as coral reefs, mangrove forests and seagrass beds.

For most small-scale fisheries, there is very little information available about their fishing effort – that is, how many fishers there are, and where, when and how they fish, as well as exactly what they catch. Without this, it’s very difficult for governments to develop management programmes that can ensure sustainable fishing and protect the ecosystems and livelihoods of the fishers and the communities that depend on them.

Small-scale fishers of Zanzibar attending their driftnets.
Per Berggren/Marine MEGAfauna Lab/Newcastle University, Author provided

While the small-scale fisheries of East Africa and the nearby islands are not well documented, we do know that there are at least half a million small-scale fishers using upwards of 150,000 boats. That’s a lot of fishing. While each fisher and boat may not catch that many fish each day, with so many operating, it really starts to add up. Many use nets – either driftnets floating at the surface or gillnets, which are anchored close to the sea floor. Both are cheap but not very selective with what they catch. Some use longlines, which are effective at catching big fish, including sharks and rays.




Read more:
Sharks: one in four habitats in remote open ocean threatened by longline fishing


In 2019, our team reported that catch records were massively underreporting the number of sharks and rays caught in East Africa and the nearby islands. With the discovery of two new species here – a global hotspot for shark and ray biodiversity – the need to properly assess the impact of small-scale fisheries on marine life is even more urgent.

Pliotrema kajae, as it might look swimming in the subtropical waters of the western Indian Ocean.
Simon Weigmann, Author provided

How many other unidentified sharks and other species are commonly caught in these fisheries? There is a real risk of species going extinct before they’re even discovered.

Efforts to monitor and manage fisheries in this region, and globally, must be expanded to prevent biodiversity loss and to develop sustainable fisheries. There are simple methods available that can work on small boats where monitoring is currently absent, including using cameras to document what’s caught.

A selection of landed fish – including sharks, tuna and swordfish.
Per Berggren, Author provided

The discovery of two new sixgill sawsharks also demonstrates the value of scientists working with local communities. Without the participation of fishers we may never have found these animals. From simple assessments all the way through to developing methods to alter catches and manage fisheries, it’s our goal to make fisheries sustainable and preserve the long-term future of species like these sawsharks, the ecosystems they live in and the communities that rely on them for generations to come.The Conversation

Per Berggren, Marine MEGAfauna Lab, Newcastle University and Andrew Temple, Postdoctoral Research Associate in Marine Biology, Newcastle University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Can buying up fishing licences save Australia’s sharks?


Christopher Brown, Griffith University and Samantha Munroe, Griffith University

The World Wildlife Fund (WWF) recently raised over A$200,000 to buy shark fishing licences in Queensland’s waters. They estimate the licences, for operating nets in and around the Great Barrier Reef Marine Park, could have been used to catch 10,000 sharks each year.

Retiring these licences is a new development in Australian shark conservation, but may also limit locally caught seafood.

But do Australia’s sharks need saving, or can we eat them? It depends on where you look.

Sustainable sharks

Sharks in general are much more vulnerable to overfishing than other fish. Compared to most fish, sharks have far fewer offspring over their lifetimes. As a result, shark populations cannot tolerate the same levels of fishing that fish can sustain.

Globally, there is great reason for concern over the status of sharks. About a quarter of all sharks and rays are threatened with extinction. The high value of shark fins in Asian markets drives a large and often unsustainable shark fishery that reaches across the globe.

Australia has an important role to play in combating this trend. Many species that are globally threatened can find refuge in the Great Barrier Reef Marine Park, which has an extensive system of protected areas and comparatively low fishing effort. Despite this potential safe haven, some species in Australia still rest on an ecological knife edge.

A white-tip reef shark in the Great Barrier Reef Marine Park.
Christopher Brown

For example, the great and scalloped hammerheads (which the WWF says will benefit from the licence purchase) are both by-catch species in the Australian fishery and are listed by the International Union for Conservation of Nature as endangered.

Australian fishermen don’t head out to catch hammerheads intentionally; most people do not consider the meat palatable. However, their hammer-shaped head is easily entangled in nets. Therefore hammerheads may be highly susceptible to any increase in fishing pressure.

Commercial fishers are legally required to have a licence. By buying the licences, WWF can limit the number of active nets in the water.

However, not all shark species are as vulnerable to fishing as the iconic hammerhead. Several shark species in Australia are well-managed. For instance, the spot tail shark is fast-growing and has many young, making it relatively resilient to fishing pressure. Many Australians regularly enjoy these species with a side of chips.

Species targeted by Queensland’s shark fishery are likely sustainable. The latest fishery assessment published by the Queensland government in 2014 found that catches of most shark species were well within safe limits.

Supporting our local shark fisheries is therefore far better than importing shark from overseas where fisheries may be poorly managed.

But it is not all good news in Australia. Both the assessment and an independent review found that while Queensland’s shark catch likely is sustainable, we need to be cautious about allowing any increases.

Importantly, Queensland’s 2014 shark assessment relies on very limited data. A crucial fishery observer program was cut in 2012. The limited data mean that regulations for Queensland’s shark catches are set conservatively low. Any increase in catch is risky without an assessment based on higher-quality data.

Scientists use tag-and-release programs to track the movements and population size of sharks. But more direct fisheries data are needed.
Samantha Munroe

A win for fishers and fish

Buying up licences in an uncertain fishery may be an effective way to prevent the decline of vulnerable species. Although buying licences is a new move for marine conservation groups in Australia, elsewhere it has proven an effective strategy for conservation and fisheries.

For instance, in California the conservation group Nature Conservancy bought fishing licences for rockfish, some species of which are endangered.

The Nature Conservancy now leases those licences back to fishers that promote sustainable fishing methods. The fishers themselves can charge a higher price for sustainable local catches of fish. What started as a move purely for conservation has had benefits for those employed in fisheries.

The lesson here is that conservation organisations can be the most productive when they work with, not against, fisheries. The recent shark licence purchase in Australia could be a great opportunity for fishers and conservation organisations to work together to maintain healthy ecosystems and fisheries.

But if Australians are serious about protecting sharks, there are other steps we still need to take. Queensland should reinstate the fishery observer program so we have reliable data to assess shark populations. For instance, currently we don’t know how many sharks are caught as by-catch in other fisheries.

A lemon shark seeks its fish prey in the shallow waters on Australia’s Great Barrier Reef. Lemon sharks are caught by our fisheries, but are not a target species.
Megan Saunders

Shark control programs designed to protect bathers are also a threat to endangered shark populations. However, data on deaths from shark control in Queensland were not accounted for in the government’s catch limits.

Accounting for these missing deaths could make a serious dent in our sustainable catch, an independent review found.

There is an opportunity to address these issues in Queensland’s upcoming fisheries management reform. Have your say here.

If conservation groups can work with fisheries, a more consistent and sustainable shark-fishing strategy may emerge. Australians can continue to be proud of our efforts to protect marine life, but can still enjoy shark for dinner.

The Conversation

Christopher Brown, Research Fellow, Australian Rivers Institute, Griffith University and Samantha Munroe, Postdoctoral research fellow, Australian Rivers Institute, Griffith University

This article was originally published on The Conversation. Read the original article.

Banning fishing has helped parts of the Great Barrier Reef recover from damage


Camille Mellin, Australian Institute of Marine Science; Aaron MacNeil, Australian Institute of Marine Science, and Julian Caley, Australian Institute of Marine Science

The world’s coral reefs face unprecedented threats. Their survival depends on how well they can cope with a long list of pressures including fishing, storms, coral bleaching, outbreaks of coral predators and reduced water quality. Together, these disturbances have caused the Great Barrier Reef to lose half of its coral cover since 1985.

One often-used way of protecting marine ecosystems is to close parts of the ocean to fishing, in no-take marine reserves. From research, we know that by reducing fishing you end up with more and bigger fish (and other harvested species such as lobsters).

But other benefits of protection might be more surprising. In a new study, we show that no-take reserves helped the Great Barrier Reef’s corals to resist a range of disturbances, such as bleaching, disease and crown-of-thorns starfish, and to recover more quickly from damage.

More exposure, but better protection

Our study used observations between 1993 and 2013 of 34 types of coral and invertebrates and 215 fish species on 46 reefs spread across the Great Barrier Reef. Among the 46 study reefs, 26 were open to fishing and 20 were in no-take marine reserves.

During the study period, several occurrences of coral bleaching, coral disease, storms and outbreaks of crown-of-thorns starfish were recorded.

The total number of disturbances affecting our study reefs increased in recent years (2010-12), mostly due to severe storms affecting the central and southern sections of the Great Barrier Reef. Among our study reefs, those located inside no-take marine reserves were more exposed to disturbance than those outside no-take marine reserves.

Our study showed that, inside no-take marine reserves, the impact of disturbance was reduced by 38% for fish and by 25% for corals compared with unprotected reefs. This means that no-take marine reserves benefit not only fish but entire reef communities, including corals, and might help to slow down the rapid degradation of coral reefs.

Damaged coral reef around Lizard Island a few days after cyclone Ita.
Photo by Tom Bridge, http://www.tethys-images.com

Faster recovery

In addition to greater resistance, reef organisms recovered more quickly from disturbance inside no-take marine reserves. After each disturbance, we measured the time that both coral and fish communities took to return to their pre-disturbance state.

We found coral communities took the longest to recover after crown-of-thorns starfish outbreaks. Outside no-take marine reserves, it took on average nine years for these communities to recover. It took just over six years inside no-take marine reserves.

Although there is more work to be done, one reason that reefs inside no-take zones are able to cope better with disturbances is that they preserve and promote a wider range of important ecological functions. Where fishing reduces the numbers of some species outside protected areas, some of these functions could be lost.

Coral reef showing signs of recovery.
Photo copyright Tom Bridge/www.tethys-images.com

Knowledge for conservation

Marine reserves (including no-take zones) currently cover 3.4% of the world’s ocean, which is still well below the 10% target for 2020 recommended by the Convention on Biological Diversity. The slow progress towards this target is partly due to the perceived high costs of protection compared to true ecological benefits, which can be difficult to gauge. While some surprising benefits are beginning to be revealed in studies like ours, such benefits remain little understood.

Our results help to fill that gap by showing that no-take marine reserves can boost both the resistance and recovery of reef communities following disturbance. In ecology, resistance plus recovery equals resilience.

Our work suggests that the net benefit of no-take marine reserves is much greater than previously thought. No-take marine reserves host not only more and bigger fishes, but more resilient communities that might decline at slower rates.

These results reinforce the idea that no-take marine reserves should be widely implemented and supported as a means of maintaining the integrity of coral reefs globally.

Our conclusions also demonstrate that we need long-term monitoring programs which provide a unique opportunity to assess the sustained benefits of protection.

The Conversation

Camille Mellin, Research Scientist, Australian Institute of Marine Science; Aaron MacNeil, Senior Research Scientist, Australian Institute of Marine Science, and Julian Caley, Senior Principal Research Scientist, Australian Institute of Marine Science

This article was originally published on The Conversation. Read the original article.

This island nation just banned all commercial fishing


Grist

The Micronesian country of Palau, which encompasses 250 islands in an area the size of France, just became a marine sanctuary.

At a recent U.N. oceans conference, President Tommy Remengesau, Jr. declared commercial fishing illegal in an attempt to protect the vibrant sea life that makes Palau a magnet for Asian vacationers. “I always say the economy is our environment and the environment is our economy,” he said. (Wise dude.)

To make up for the lost revenue, Palau will tout its appeal for ecotourism, snorkelers, and scuba divers.

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