Pollock fishing may be the cause of Bering Sea fur seal decline, study finds
Fur seals are an essential subsistence food for the Unangax̂ communities of the Pribilof Islands of the Bering Sea. But for years scientists have been unable to explain why seal populations have declined.
Now, a new study points to an industry that has long been suspected, but never definitively linked to population decline: the massive commercial pollock fishery in Alaska, which harvests the same species that lactating females depend on to feed their young. .
Jeffrey Short is the lead author of a study published in the Journal of Marine Science and Engineering September 9, which he says presents for the first time clear evidence linking pollock fishing to fur seal reduction.
Some scientists have suspected pollock fishing, but factual research linking the two has been scarce. According to Short, this is because much of the existing literature has focused on the overall abundance of pollock, which is quite high.
However, this new study focuses on pollock catches, that is, the quantity of fish removed from the water.
“I was just amazed at how well it worked,” Short said. “This single number of pollock catches can explain almost all of the [fur seal] demographic trajectory since the mid-1970s.
The team found evidence to suggest that the pollock industry, by breaking up the dense schools of fish that mothers rely on to fatten their young, made it harder for lactating fur seals to feed their young.
“What a lactating female fur seal wants to do is find a dense aggregation of food right next to where her cubs are,” said Short. “So that she can spend the minimum amount of energy going to find it, sit on it and eat as she likes, then swim right away and nurse her puppies and repeat that all summer.”
But commercial fishing boats also seek out dense schools of fish. By fishing these schools, the fleets break them and the fish disperse. This means that the mother seal cannot fatten her young as quickly as before.
This is a problem because the puppies swim south in the fall. If they haven’t built up enough reserves, these baby seals are unlikely to survive their first year.
And that is, according to this study, the reason why fur seal populations are declining so sharply.
The number of northern fur seals in the Bering Sea has fallen by around 70% since the 1970s.
“I think it’s possible that the fur seal herd will eventually disappear or disappear from the Pribilof Islands,” Short said.
The fur seal colonies of the Bering Sea are of particular importance to the Unangax̂ communities of the Pribilof and Aleutian Islands, who depend on sea lions for their livelihood.
Martin Stepetin grew up on Île Saint-Paul – the most populous of the Pribilof Islands – but now lives in Juneau where he Alaska Native Advocates.
“We eat these seals, so it’s getting scary,” Stepetin said. “If you’re trying to support your family and trying to put food in the fridge, you worry about the future. What about your children? How much food will there be each time your children are of age? Will they be able to provide for their families?
The study suggests that to make any real change, the fishery – which is one of the most lucrative in the United States – would likely have to limit pollock catches to around one million tonnes in areas around the Pribilof Islands. This is almost a quarter of the total of 1.375 million tonnes currently authorized.
Pollock industry propellant Stephanie Madsen said she was concerned about a one-size-fits-all solution.
“It would be devastating to have just one blunt tool. And that’s what I think it is. It’s a blunt tool, ”said Madsen, executive director of an industry group that represents large factory trawlers, the At-sea Processors Association.
Madsen said she welcomes the document in the growing body of research on the topic, but said there had to be more precise measures than simply limiting the total allowable catch. She also expressed skepticism that limiting catches would improve the plight of seals.
“When you talk about drawing circles around rookeries and preventing fishing from happening there, you make several assumptions that pollock stays inside that circle, that fur seals don’t go. get out of the circle, ”Madsen said.
The pollock industry employs approximately 30,000 people across the country. In the eastern Bering Sea and Gulf of Alaska, fishing grossed about $ 420 million in 2020, according to the National Oceanic and Atmospheric Administration.
“Thousands of jobs and tens of thousands of families depend on this income,” Madsen said. “I think depending on the size of those circles, for the most part, it could be quite detrimental to the pollock fishery’s ability to harvest our quota.”
Madsen said that while she is moderately concerned about the authors’ findings, she does not anticipate that they will lead to any immediate changes in the industry.
The North Pacific Fisheries Management Board, which manages the fisheries in the region, receives marine mammal updates at the start of each year.
“We have great science, we have rational thinking heads,” Madsen said. “And I think the North Pacific Council will take this information [when] they receive their annual marine mammal updates at the february board meeting.