Plankton predator: 250 animals tracked on world’s biggest tagging project
IRISH WATERS may be home to a very high proportion of the world’s basking shark population – the second largest fish in the sea.
Scientists attending an international shark conference in Galway have been presented with data suggesting thousands of the sharks frequent this coastline.
“When you consider global estimates of basking shark populations amount to only 20,000 individuals, this means a high proportion of the world’s basking shark occur in Ireland, or global estimates are horribly wrong,” Irish basking shark study group leader Dr Simon Berrow said.
“Since 2008 we have tagged nearly 250 sharks in what is now by far the biggest basking shark tagging project in the world,” Dr Berrow said in his paper to the 14th European Elasmobranch Association conference.
“These tagging studies have also enabled us to estimate the number of sharks in an area,” he said, outlining work funded by the Heritage Council and carried out with National Parks and Wildlife Service ranger Emmet Johnston.
“In 2009 and 2010 we estimated that around 200 sharks occurred in Trawbreaga Bay off the Inishowen peninsula, Co Donegal,” Dr Berrow said.
“During this period, basking sharks were also being reported in many bays and off headlands all around the Irish coast, suggesting there were thousands of sharks [off] Ireland,” he said.
The group has pioneered a method of obtaining shark samples for genetic and other analysis, such as the effects on them of pollution, without killing the animals.
Recalling that the sharks were once killed in large numbers in Ireland, mainly for their liver oil, Dr Berrow said they were excellent indicators of climate change.
“Basking sharks fundamentally go where zooplankton concentrates, and filter huge quantities through their gill rakers. As zooplankton distribution will be affected by climate change, the distribution, abundance and movements of sharks will change to reflect these trends,” he said.
“Tracking basking sharks may be far more effective than tracking zooplankton, and [may] provide one of the best indicators of the health of our seas and thus the planet,” he pointed out.
Conference organiser Dr Edward Farrell of the Marine Institute in Oranmore, Co Galway said the enormous diversity in Irish waters was reflected in the sharks present, of which there were at least 28 species, along with some 18 species of ray and skate.
Elasmobranch (shark, ray and skate) experts from all over the world attended the two-day event at the institute, focusing on new research and on threats to fragile shark populations.