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Sharks and Rays Back in the North Sea!

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Sharks and Rays Back in the North Sea! SHARKS AND RAYS BACK IN THE NORTH SEA! © Peter Verhoog Juvenile thornback rays ABOUT SHARKS AND RAYS Important for the marine ecosystem Long before we humans walked this earth, beautiful sharks and rays were swimming in the world’s oceans. These apex predators have been at the top of the food chain for 450 million years, where they fulfil a vital role in the ecosystem of the oceans. They ‘maintain’ coral reefs, they ensure the ecological balance between species and they contribute to healthy populations of other animals by eating the weaker individuals. Largescale overfishing of sharks and rays affects the entire food chain and thus the health of the oceans. Low reproductive capacity Sharks and rays are characterized by a low reproductive capacity; many species are only sexually mature after more than 10 years. Most shark species develop their eggs inside the body of the female. Baby sharks are born fully developed. Most sharks have 1 to 20 pups per year. The reproductive biology of sharks is therefore more akin to that of marine mammals than fish. The Dutch North Sea is the habitat of several egg-laying shark species and rays: both the small-spotted catshark and the greater spotted dogfish or nursehound lay 18 to 20 eggs per year. The eggs take 7 to 10 months to hatch. The empty cases often wash up on beaches. Most Dutch bottom-dwelling rays lay eggs, from 20 to 140 eggs per year. Due to their low reproduction cycles, sharks and rays are vulnerable for overfishing, as the recovery of populations is very slow. Marine Strategy Framework Directive (MSFD) In its policy for the implementation of the Marine Strategy Framework Directive (MSFD), the Dutch government has stated that in the Dutch part of the North Sea, the population size of vulnerable fish species such as sharks and rays must increase. Reversing a long-term negative trend in elasmobranch stocks must be facilitated by working on the recovery of habitats and by reducing bycatch. © Peter Verhoog Angel shark 2 © WNF Juvenile spurdog Threatened with extinction Worldwide, a quarter of all sharks and rays are threatened with extinction (IUCN 2016, Red List of Threatened Species). In European waters, more than 30% of species are endangered. At the beginning of the 20th century, rays and skates were frequently found in the Dutch North Sea. Some species were intensively fished for consumption. When the Southern Sea was closed off in the thirties, an important juvenile habitat for sharks and rays was lost. Their numbers steadily decreased, until sharks and rays became rare in the southern North Sea after the Second World War. Due to the intensification of the fisheries in the North Sea from the fifties onwards and the use of heavier fishing gear, more and more areas have become accessible to fisheries. Because of this, these areas are no longer a refuge for sharks and rays. Presently, only two species are regularly caught: the thornback ray and the spotted ray. The angel shark and the shagreen skate are probably extinct in the Dutch North Sea. Ten out of the twenty shark and ray species that still occur in the North Sea are on the IUCN Red List of threatened species. Most sharks and rays and their habitats are not protected. Better protection needed The habitats and nursery grounds for sharks and rays are insufficiently known and must be better charted and protected. Shallow breeding grounds such as coastal zones can become a refuge. Currently a joint project is being worked on with the Dutch fishing organizations that focuses on recognising catches, the survival of the caught animals and on monitoring the number of sharks and rays that are caught. Use is made of (automated) video image recognition and an innovative DNA method. With the information gathered from these methods and the estimated size of the populations, the effect of the fishing industry on the rays in the North Sea can be determined. This will enable us to advise on sustainable management of shark and ray species in the North Sea. 3 SHARKS AND RAYS BACK IN THE NORTH SEA! Reintroduction The numbers of sharks and rays have decreased to such an extent, or have even completely disappeared, that natural recovery of the population not seems feasible. The odds that they will return to the North Sea on their own accord is slim. Reintroducing sharks and rays which are (lo- cally) extirpated in the North Sea (such as the angelshark and the common skate) could possibly be the only way to reinstate these species in Dutch waters. Due to the slow reproductive capacity of sharks and rays, we have developed a long-term plan. Policy must also be adjusted to the long- term. The pilot programme for reintroduction is divided into three phases, the reintroduction of the thornback ray is currently in phase three, the other species are in phase two.. There are several shark and ray species in the North Sea that are eligible for a reinforcement pro- gramme. The thornback ray (Raja clavata), still quite rare in Dutch waters, is already being bred in captivity. There are also other eligible species. Among other things, we consider which species are locally extinct and which species are suitable for breeding. For species that are not yet available through the aquaria, we will ask fishermen and (inter)national research institutes to supply eggs that they find in their fishing and research nets. Phase 1: Setting up of aquaria In cooperation with aquaria and zoos we have equipped Breeding Centre Blue Linked with tanks to breed thornback rays. Genetic research has shown that the cultures fit the profile of the population that is still present in the wild. We will also seek cooperation with foreign zoos and aquaria that have experience with breeding and caring for sharks and rays. Phase 2: breeding programme Thornback eggs have been successfully reared at the Breeding centre Blue Linked in Utrecht. The next step will be to breed distinct species of viable sharks and rays from the collected eggs. In view of the successful breeding of rays in Dutch aquariums, we expect this to be a viable option. Both the breeding and the reintroduction programme will be set up in accordance with the IUCN Guidelines for Reintroductions and Other Conservation Translocations of the IUCN/SSC Re-Intro- duction Specialist Group (RSG) and will be made visible to the public. A week after the thornbacks have been tagged they will be returned to the former oyster pits in Yerseke to acclimatise in Ooster- scheldewater. Their well-being is checked there daily. After two weeks the animals can be released into the Oosterschelde. Phase 3: pilot release programme From the report ‘A habitat suitability analysis of the Oosterschelde and the Voordelta for the thorn- back ray (Raja clavata) in the Oosterschelde and the Voordelta’, it appears that these areas are potentially suitable as a habitat for the thornbacks. Taking into consideration assumptions and uncertainties, testing the conclusions through monitoring the released thornbacks with special tags (electronic data storage tags) is a necessary step in the development of knowledge about the thornbacks in the Oosterschelde and the Voordelta. This approach can also serve as an example for the habitat suitability analysis for other species of rays and sharks in this area. The first bred and tagged animals were released in the Oosterschelde in October 2017. The released rays are carefully monitored. For the (acoustic) tagging and monitoring of the rays, we collaborate with project part- ner Sportvisserij Nederland, which has been running a tag and release programme for sharks and rays in the Zeeland delta since 2012. The knowledge we have gained through this research and the reintroduction programme for sharks and rays can be used in worldwide reintroduction programs. 4 © Peter Verhoog Nursehound Sustainable fisheries There is no targeted catch of sharks and rays in the Netherlands. The large problem, however, lies with the catch and bycatch of sharks and rays. The animals are mostly thrown back into the ocean, sometimes already dead. Dutch fishing policy for the coast and the inland waterways is aimed at a more sustainable fishing sector. Part of this policy is the ‘discard ban’: a ban on throwing fish back into the ocean. This ban does not include the species that are not allowed to be fished according to EU legislation, such as the endangered shark and ray species. These must still be released prompt- ly and unharmed. This exception does however not apply to all sharks and rays, and species that are not (yet) threatened can still be caught and landed. The discard ban is being introduced in phases, and it is possible to obtain an exemption for species with a high survival rate, such as sharks: they can easily survive being put back. More research is needed on rays, research that is currently taking place. An obligation for sharks to be released can aid the slow recovery of the species. We are committed to helping fishermen to achieve better recognition at species level and the importance of correct handling on board. Monique van de Water, World Wide Fund for Nature the Netherlands: “The common skate is a ray with a width of more than two meters. The tope shark can also grow to a length of 2 metres and was quite common in the North Sea in the past. I think it would be fantastic to see these magnificent, large marine creatures swimming in the North Sea again. The World Wide Fund for Nature works globally to protect sharks and rays. These animals are crucial for the health of our oceans.” 5 Protection and policy With some exceptions (porbeagle shark, spiny dogfish and the common skate), many species in the North Sea are currently not sufficiently protected.
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