In the early 1990s the world’s second largest fish the basking shark, reaching up to 12 m in length, was still being exploited commercially for meat and oil in the northeast Atlantic, as it had been for the previous two centuries. The increased trade in shark fins for shark fin soup in the Far East was also having an effect as the very large fins of the basking shark commanded among the highest prices, up to £10,000 per fin. There were broad concerns that population levels were low and still declining. However at the time, the basking shark was Red listed by the IUCN (International Union for the Conservation of Nature) as ‘Insufficiently Known’, so proposals for its conservation under international agreements did not succeed given the lack of basic knowledge of its biology and ecology.
The basking shark, the world’s second largest fish, has been commercially exploited for food and oil for over 200 years. Photo: J. Stafford-Deitsch.
In 2001 basking shark migration was studied for the first time by MBA researchers Prof David Sims and Dr Emily Southall using new satellite-linked archival transmitters capable of monitoring shark movements and behaviour continuously over many months. Funded primarily by the UK Department for Environment, Food and Rural Affairs (Defra) the research achieved a world first by tracking basking shark movements over long distances and across seasons including through winter.
Sims and Southall demonstrated basking sharks were active in winter and were feeding on overwintering zooplankton in deeper waters, thereby dispelling the “hibernation” idea that had stood for some 50 years. Importantly they showed sharks were highly migratory, travelling thousands of kilometres in a few weeks, diving to nearly 1km down, but at the same time remaining faithful to rich feeding areas on the continental shelf and shelf-edges of the northeast Atlantic where they were tagged.
The research informed a key re-interpretation of the basking shark catch declines seen worldwide during the 20th century: the data indicated basking sharks were regionally site attached to productive areas with limited emigration, which meant area-focused fisheries could potentially overexploit the population, suggesting observed catch declines may reflect regional abundance changes. Following this research, conservation proposals for basking shark employed the new results in this way.
The UK Government through Defra’s Global Wildlife Division working with MBA researchers incorporated the new results and interpretations into its 2002 proposal to attain listing of basking sharks on Appendix II of the Convention on International Trade in Endangered Species of Fauna and Flora (CITES). Appendix II requires international trade in these species is monitored through a licensing system to ensure that trade can be sustained without detriment to wild populations. A previous attempt by the UK in 2000 to list the basking shark on Appendix II had failed, prior to the MBA research being undertaken. However in November 2002 at the CITES Conference of Parties (COP) meeting in Santiago, Chile, the UK Government-led proposal for basking shark Appendix II listing was passed by a two-thirds majority (effective from February 2003).
“Our research has shown that basking sharks are migratory which means only international protection from unregulated international trade will work.”
“This result is a victory for all of us and I'm proud of the UK team here and the quality of our scientists and officials.”
UK Government Minister for Environment, 15 November 2002, CITES COP, Santiago, Chile
Building on this work, Prof Sims and Dr Southall went on to show that basking sharks moved regularly across many national boundaries before coming back to ‘home’ areas. This research underpinned the UK-led proposal in November 2005 to list basking sharks on Appendix II of the Convention for the Conservation of Migratory Species of Wild Animals (CMS; the Bonn Convention). The UK proposal was successful largely due to the MBA’s research and strengthened protection measures in international waters; listing under the Convention means that nation states with basking shark populations must work with adjacent member states to introduce strict legislation to prevent capture and landing of the shark.
“The success of the proposal was largely based on recent research by the Marine Biological Association which showed that basking sharks migrate over large distances between the waters of many countries.”
UK Delegation to the CMS Conference of Parties, 25 November 2005
The research has contributed to the basking shark becoming one of the most protected species of shark that in itself has taken on the role of a conservation flagship, helping open the way for other successful proposals and listings of threatened sharks that have been achieved since then.
After some 15 years of protection it is now thought basking shark numbers in European waters are recovering.
Funding provided by Defra and NERC.