During the summer of 2004 a survey of cetacean distribution and relative abundance was conducted on board the RV Celtic Explorer off the west coast of Ireland.
508 hours of survey effort were conducted, with 304.2 hours in Beaufort sea-state 3 or less. Two hundred and thirty one sightings of eight species were recorded.
These species were: Common Dolphin, Atlantic White-sided Dolphin, Bottlenose Dolphin, Harbour Porpoise, Risso’s Dolphin, Pilot Whale, Minke Whale and Fin Whale. In all 2,933 animals were counted.
The greatest diversity and relative abundance were recorded on the Rockall Bank, where Atlantic white-sided dolphin was the most abundant species. Common dolphins were the most abundant species recorded on the continental shelf to the south-west of Ireland. The relative abundance of cetaceans off the north coast was very low, despite the most effort being put into surveying this area.
The results show that the seas off Irelands west coast are not just one big pool of water where you have an equal chance of encountering any dolphin, where ever you go. Instead the seas cover a variety of habitats as different as any found on land and as we move from shallow waters of the Atlantic shelf to the deep waters of the abyssal plains and up the slopes of the offshore banks far off our west coast, the variety and abundance of marine mammals changes.
The results have implication for the way in which we manage our oceans in order to conserve the biodiversity of mammals in our seas. We have to manage habitats and ecosystems, not just species as one cannot survive without the other.
The paper also highlights the success of surveys based on Ships of Opportunity and the IWDG will continue its program of ship based surveys this year with Autumn and Winter surveys planned on board the Celtic Explorer and with the Irish Navy.
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