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Tracking Basking Sharks with Photographs – from France to Norway?

By Cat Gordon, 27th August 2012

This year our Basking Shark Project has focused on applying the methods we have developed for recognizing individual sharks from high quality photographs on a wider scale. We have been comparing data collected in different regions, and in different countries. And in the last month we have visited northern Norway, at the northern end of the species range in Europe, to search for individuals already recorded further south.

The work of comparing photographs, and looking for matches from within a very large and still increasing database, is repetitive and extremely time consuming. It does however have moments of excitement, such as when clear matches are found from photographs taken hundreds of km apart, as Chris Dick has found when twice he detected a match between individuals photographed four years apart. Chris is the Heriot-Watt University graduate student, who has been helping with the project this year. One of the sharks he detected was recorded on the first occasion in Scotland, and on the second in France, and his other shark on the first occasion in South-West England, and on the second occasion in Scotland. These re-sightings support the impression of the seasonal movements of the sharks that we have gained from satellite tagging, that individuals move very widely but tend to move from France and England to Scotland as summer proceeds.

Most recently, to see if we can extend this pattern of observations further to the north, Mauvis (Dr. Mauvis Gore, the project leader within Marine Conservation International) just recently visited Norway to survey for and take identification photographs of basking sharks. There we have been collaborating with Dr. Claudia Junge, (based at the Norwegian Institute of Water Research and the University of Oslo).who is leader of the Norwegian Shark Alliance (HAI Norge). Claudia and HAI Norge established a basking shark reporting scheme in Norway in 2009 and assisted with our joint work both by organising facilities and recruiting volunteer boat crew. The plan worked extremely well, the weather was unusually good, and the Lofoten Islands where the survey work based proved quite beautiful and full of wildlife. Excitingly, yet disappointingly, the team actually saw more Orca (killer whales) than basking sharks, adding an extra dimension to the problem of distinguishing fin types!

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