A five-metre basking shark that spends its summers in Lough Foyle and near Malin Head has been detected off the western coast of Africa.
Head of a Basking Shark (Cetorhinus maximus)
‘Banba’ a female basking shark tagged in July with a satellite transmitter off Malin head, Co. Donegal has just released its transmitter west of the Cape Verde Islands, over 5000km away from were it was originally tagged.
The movement by the shark ‘Banba’ into warm tropical waters off West Africa coupled with similar findings by Mattew Whitt working with Scottish Natural Heritage and leading American shark biologist Greg Skomal in the western Atlantic, questions the validity of the established theory that basking sharks inhabit temperate waters only.
Previous basking shark tracking studies undertaken in the northeast Atlantic have only recorded shark movements within temperate waters.
The majority of tracked sharks have displayed a seasonal onshore-offshore migratory pattern, with movements of one or two hundred miles offshore onto the continental shelf edge during winter and return shifts to coastal waters during summer months.
This seasonal pattern allows the sharks to feed year-round on copepods a type of zooplankton, their stable food source. However, the recording of this magnificent journey by a basking shark from Malin head to warmer tropical waters questions many of the fundamental theories marine biologists have regarding the species and its lifecycle.
Understanding where the sharks are and what they do when they are there, is essential to making informed management decisions regarding this endangered species.
—Emmett Johnston
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