The West Coast of Ireland is the first place in the world where the annual reproductive behaviour of basking sharks has been seen.
“It is astonishing that this wonder of the natural world has remained hidden for so long,” according to Professor David Sims, Senior Research Fellow at the University of Southampton and lead author of a study carried out by biologists from the Marine Biological Association and the Irish Basking Shark Group.
It has revealed “the global importance of the West Coast of Ireland for the endangered species.”
Circling formations have been documented on a few occasions over the past 40 years in the North-West Atlantic off Canada and the USA. But although basking sharks are often seen filter-feeding plankton in the UK and Irish coastal waters during the summer, the circling formations were rarely seen. Until now, scientists could not explain the behaviour.
Using underwater cameras and aerial drones off County Clare from 2016 to 2021, scientists got video footage of 19 circling groups. Each comprised between 6 and 23 sharks swimming slowly at the surface, with others deeper down.
“This research has shown the importance of Irish waters,” says Dr Simon Berrow of the Atlantic Technological University, Galway and the Irish Basking Shark Group, who co-led the research: “How usually solitary basking sharks find a mate in the ocean’s expanse has been an enduring mystery. Our discovery of these basking shark grounds in our coastal waters makes it more urgent that this species gains protection in Irish waters from potential threats, such as collisions with marine traffic and the impact of offshore renewables.”
Legislation to protect basking sharks in Irish waters was drafted this year, although they are protected in many parts of the world. It remains to be signed into law.
