IN their quest for food, humans do not recognise that all creatures are entitled to their share of Earth’s resources. Overfishing can deprive ocean predators, including whales and dolphins, of food.
This has been highlighted in new research by Irish scientists.
Whale-watching is a popular pastime in Ireland and, following regular sightings of the fin, humpback and minke species close to shore in the last 10 to15 years, there has been a resurgence of interest in whales. West Cork is a hotspot.
Whales are massive and have commensurate appetites. Some can consume between six and seven tonnes per day. From June to February, between Slea Head, Co Kerry, and Hook Head, Co Wexford, whales follow the seasonal movements of sprat and herring, as they congregate inshore to spawn.
The latest research provides the first information on the diets of fin and humpback whales in Ireland for 100 years. Fin whales in Irish waters have a diet comprising 50% krill (a small shellfish) and 50% young sprat and herring. In European waters, fin whales feed exclusively on krill, so the Irish whales are unusual in relying on small fish.
Humpback whales prefer sprat and herring when feeding in Irish waters and their diet comprises less than 30% krill. The research team examined the long-term diet of whales by analysing baleen plates — flat sheets of fingernail-like tissue in the mouths of large whales, used to filter food from seawater.
The Irish Whale and Dolphin Group, the Galway-Mayo Institute of Technology, and the Marine Institute worked together on the project to determine the feeding habits of these whales.
The information is essential if we are to adopt a more sustainable approach to managing our fisheries. An ecosystem approach should recognise that there are predators, such as whales, other than humans in the sea, and these are entitled to their share of marine resources. However, this is not always understood.
“We now have clear evidence that sprat and herring are important species supporting whales in Irish waters, and we must manage our fisheries with this in mind,’’ team member, Dr Conor Ryan, says.
“We are very worried that sprat is being fished with an open quota, despite a huge gap in our knowledge about the life history of this important species in the Celtic Sea,’’ he says.
The message is that whale-watching has the potential to grow and benefit coastal communities, if fish stocks are managed with both human and marine predators in mind.
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