New scientific research published today explores how sharks, skates and rays are distributed around Scotland’s coasts, with the results to be used to help their conservation.
Using existing information about shark, skate and ray distribution around Scotland, a new report models where the highest numbers of nine threatened species are predicted to occur.
The report also assesses the sensitivity of sharks, skates and rays (collectively called elasmobranchs) to various fishing methods and predicts bycatch hotspots – the areas where incidental capture of elasmobranchs is most likely – in prawn and scallop fisheries.
The scientists involved have predicted where the highest numbers and variety of sharks, skates and rays occur and overlaid these with the areas where bycatch is predicted to be most likely, revealing areas where conservation measures could have the greatest impact for these species.
This new evidence will support the development of an elasmobranch action plan for Scotland and may influence future fishery management measures to protect this threatened group of fish. All species of sharks and rays are on the OSPAR list of Threatened and Declining Species.
NatureScot’s elasmobranch specialist, Dr Jane Dodd, said, “Conserving and restoring sharks, skates and rays is difficult because we have limited information about their lives. This exciting research gives us much more insight into where the sharks, skates and rays are around Scotland’s coasts and the fishing activities they are sensitive to. We now plan to speak to fishers to learn more about their interactions with elasmobranchs.
“Research like this is vital, since all species of sharks and rays are identified as threatened and declining due to historical overfishing – and their recovery will likely be hampered by habitat damage and climate change. They depend on a healthy marine environment to ensure they have abundant prey, such as shellfish, crustaceans and fish and as top predators can act as indicators of ecosystem health.”
Elasmobranchs differ from other fish because they have a skeletal structure made from cartilage as opposed to bone. They range throughout the oceans and can be found in all oceanic and coastal zones. Scotland has over 30 species of sharks, skates and rays recorded in its waters of which 25 are found in coastal waters.
All elasmobranchs share characteristics which make them vulnerable to overfishing and their populations take a long time to recover once reduced. Elasmobranchs are slow growing, late to reach maturity and typically have low fertility, so the number of individual fish recruited into a population annually is low. Many species are also vulnerable to habitat disturbance and loss.
The research modelled the distribution of nine species by combining data from multiple sources, including experimental fishing and baited camera surveys. The species covered includes the following skates and rays: flapper skate, cuckoo ray, spotted ray, starry ray, thornback ray; and the following sharks: spurdog (also known as spiny dogfish), black mouth dogfish, lesser spotted dogfish, and starry smooth hound.
The report, led by the Scottish Government’s Marine Directorate and published by NatureScot, also found that seven out of the nine species show preferences for depths of 100m or deeper, which explains their predominance on the west of Scotland, where deep trenches can be found close inshore and within sea lochs. Species with either a preference for shallow depths, such as cuckoo rays, or no particular depth preference, such as spotted rays, were commonly found in the North Sea, to the east of Scotland.