A shark tagged near the mouth of Lough Foyle last summer has headed to the West African coast on its winter holidays, it’s been revealed.
Banba, a female basking shark tagged in July with a satellite transmitter off Malin head, has been tracked off the coast of the Cape Verdi Islands, west of Senegal and more than 5000km away from where it was originally spotted.
Experts say the movement of Banba has confirmed for the first time where the big fish travel to for warmth during the northern hemisphere in winter.
The research was carried out by the Irish Basking Shark Project, whose co-ordinator, Emmett Johnston, said the detection was something of a breakthrough, although he added that it may be “a bit premature to be rushing out to change the shark biology books”. He said his team must wait for the “pop-off” of the remaining satellite transmitters attached last summer - five basking sharks were tagged off Inishowen - before making conclusions.
“Until then there is not much we can say other than this is a highly unusual place to find a species that is presumed to inhabit temperate waters.”
He added: “Up until now there have been lots of different theories put forward about the sharks and one was that they hibernated over the winter because there wasn’t enough food in the waters around the north Atlantic. Other people said they went offshore and they have been tracked offshore in the winter.
“But we have been theorising that they head further south to where the food is, like the larger whales from this area.
“The unusual thing about this is the type of food that they eat.
“It is mainly a type of plankton, insects that are in the sea, but that is not found down there in the tropical waters.
“It is a very different kind of habitat, it is akin to finding a polar bear in the desert.
“It is in stark contrast to the type of waters that they are associated with, like the temperate waters you find up here.”
Banba, a female basking shark tagged in July with a satellite transmitter off Malin head, was one of five basking sharks tagged as part of the Monster Munch Basking Shark Community Awareness Project run by the Irish Basking Shark Study Group in association with the Inishowen Development Partnership and Queen’s University Belfast.
The movement by the shark ‘Banba’ into warm tropical waters off West Africa coupled with similar findings by 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 north east 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.