Do seals compete with commercial fishermen?

Do seals compete with commercial fisheries? @bberwyn photo.

New UK study tries to answer the age-old question

Staff Report

Like in other countries, some Irish fishermen have been complaining that seals are increasingly eating up valuable commercial fish stocks, but a new scientific study says that’s generally not the case, with the possible exception of wild Atlantic salmon.

The work done by researchers with Queen’s University Belfast, Northern Ireland, shows that seals don’t have a significant impact on herring, mackerel, cod, haddock, whiting and 30 other species caught for commercial purposes along the south and west coasts of Ireland, from counties Galway to Waterford.

But the hungry marine mammals do search out wild Atlantic salmon caught by fishermen in river estuaries. The researchers seemed to be sending mixed messages as they released the results of their findings, in a time when some commercial fishermen have called for culling seals.

“We need to emphasise that this work in no way says that seals cause no problems for the fishing industry,” said lead researcher Dr Keith Farnsworth from Queen’s University’s Institute for Global Food Security.

“They do create significant problems for static fishing gear, such as the fixed nets used by estuarine salmon fishers, and they may also impact on numbers of wild salmon, although most salmon eaten on these islands is farmed,” Farnsworth said.

“What we are saying is that for most commercially fished species off the south and west coasts of Ireland – herring, mackerel, cod, haddock, whiting and 30 other species – seals are having no significant negative effect on numbers,” he added.

The study showed seals are eating much smaller fish than the larger, mature specimens that fishermen are required by law to catch. Additionally, Farnsworth said seals may actually be helping maintain some fisheries by eating predators.

“What this work shows is that the only way to really resolve questions like this one is to be able to actually look at the detail, and work out what is going on,” said professor David Reid, explaining that the team’s research looked at the gut contents of the seals and the fish, through seal ‘scat’, to samples taken from commercial catches and research vessel surveys, and elaborate mathematical models.

The idea of seals being direct competitors with the fishing boats for the fish out there intuitively seems pretty obvious. But actually, in this case, it is not really true. They both ‘eat’ fish. But not the same fish, and they do not compete with each other.

“This is not to say that seals do not compete with fishermen in other ways. In other recent work we showed that fishermen who use set nets round the coast of Ireland can lose fish straight out of their nets to seals. But as with this study, we needed to go into the detail, and get our hands dirty to prove that.”

The findings of this new research are based on data from an area roughly 100 miles off south and west Ireland, encompassing the coastlines of counties Waterford, Cork, Kerry, Clare and Galway. The data was collected from seal droppings of both grey and common seals and collated by researchers from University College Cork.



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