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Basking Sharks really are the gentle giant of the oceans. They regularly grow up to 10m long but lead a relatively passive existence; they feed by opening their metre-wide mouth and swimming at a rate of two knots, extract various species of plankton through their gills. The plankton of choice are the energy-rich Copepods, which are spread throughout the world and may form the largest biomass of animals on the planet.
The sharks migrate into UK waters at the end of spring. They are attracted to the burgeoning food stocks that come with the arrival of the Ushant front, which pushes fingers of warm water into cooler inshore waters, bringing nutrients to the surface. Attaching satellite tags to a number of sharks has revealed stunning new insights into the behaviour of these sharks. Dr David Sims and his team from the Marine Biological Association, showed that in areas where warm and cold water meets, the sharks were rising to the surface by day and returning to the depths at night - reflecting the activity of their plankton prey.
Before the work done by Dr Mauvis Gore and her colleagues at the University Marine Biology Station, Millport, it was thought that Basking Sharks swam south in autumn but remained on the continental shelf around Europe. However, last week new research has shown that Basking Sharks migrate much further.
By tagging one female called Tracey, Dr Mauvis Gore and her team finally discovered what happens to Basking Sharks when they leave UK waters. 82 days after a tag had been put on this particular female shark off the Isle of Man, a transmission was received from off the coast of Newfoundland. Incredible! Apparently this single female has broken all known records when it comes to shark movements. She covered 9,000 km, which is three times further than any other known journey and at a depth of 1264 m. Now the only remaining mystery is why they do this?
Further Reading:
Next report: Why do Basking Sharks migrate to the UK?
Manx Basking Shark Watch