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Study reveals basking sharks tagged in Isle of Man waters to be true global citizens

This week we are highlighting recent work by early career researcher Haley Dolton and others on basking sharks in Isle of Man waters. Haley is currently a PhD researcher at Trinity College Dublin, and will be continuing her work on basking sharks in Ireland. For more information about her and this project, read on!

The Manx Basking Shark Watch (MBSW) team and scientists from the University of Exeter have revealed that basking sharks that visit Isle of Man waters are true global citizens, with tagged individuals traversing and returning to the waters of multiple countries. Satellite tracking data revealed that basking sharks tagged in Manx waters by MBSW travelled to the waters of Scotland, Ireland, France, Portugal, Spain, and the Faroe Isles, and for the first time to the waters of Morocco and Norway.

The satellite data were analysed by conservation biologists at the University of Exeter in close collaboration with MBSW. The research revealed that some basking sharks return to the same place a year later, with four sharks returning to the Isle of Man and Irish waters and one shark returning to Moroccan waters to overwinter. These insights are important as they reveal regions might be crucial for basking shark survival as they likely provide suitable habitats for feeding, breeding or pupping.

There are many barriers to basking shark survival as they undergo regional and international movements. Basking sharks face a range of potential threats during their lifetimes, such as vessel strike and accidental capture in fisheries alongside newly emerging potential issues, including plastics, electromagnetic fields from subsea cabling and noise pollution. For example, during this study, one 7.5m tagged female basking shark was accidentally caught in fishing nets in the Celtic Deep, Wales. The tag was returned to MBSW and the shark successfully freed itself from the net.

Marine protected areas could provide a ‘safe haven’ for these travelling sharks. The Isle of Man is known as a basking shark hotspot and in 2018 the Isle of Man Government announced the designation of nine new marine reserve areas, with basking sharks being one of the species they wished to conserve. Findings from this current study were however not available during the designation process, but highlight that spatial protection for the basking shark could be increased as most tracked individuals remained within three nautical miles of land (within the Isle of Man Government’s fishery zone).

The Isle of Man has always led the way in basking shark conservation, being the first jurisdiction to offer them protection. With the incorporation of the results from the study, led by Manx Basking Shark Watch and the University of Exeter, and the newly designated marine reserves, the Isle of Man is well placed to aid in the conservation of these true global citizens.

The project was financially supported by the Manx Lottery Trust, DONG Energy, Tower Insurance and the Isle of Man Bank. Boat work was funded by and scientifically licensed by, the Department of Environment, Food and Agriculture (DEFA).

Graham Hall of the MBSW team tags a basking shark with a SPOT tag. Video by: Natasha Phillips


Researcher highlight: Haley Dolton's research interests focus on the marine ecology and biology of marine vertebrates; specifically, establishing actual distribution patterns and drivers of migration. This data is acquired through the use of biologging technologies such as satellite tracking and internal temperature recorders to aid in the understanding of animal distribution and the underlying reasons for such movement. She graduated from Oxford Brookes University in Biology (BSc. Hons.) before volunteering and working for Manx Basking Shark Watch and the Manx Wildlife Trust on the Isle of Man. There she aided in the deployment of satellite tags, photo identification and DNA sampling of basking sharks. Haley also co-founded a marine research non-for-profit, The Manx Society for Marine Conservation, which had many research projects, including collecting marine megafauna sightings data from platforms of opportunity. Her master's degree at University of Exeter (with the support of the Manx Basking Shark Watch and under the supervision of Dr Matthew Witt and Dr Lucy Hawkes) culminated in a thesis entitled, 'Assessing the importance of Isle of Man waters for the basking shark Cetorhinus maximus'. This was published in Endangered Species Research. Haley is currently a PhD student at Trinity College Dublin, supervised by Dr Nicholas Payne and co-supervised by Dr Andrew Jackson and IBSP researcher Dr Jonathan Houghton. Through funding provided by the Irish Research Council, She will be researching three species in Ireland: the sixgill shark, Atlantic bluefin tuna and the basking shark.

If you'd like more information or to contact Haley:

Twitter: @haleydolton

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