For years, scientists couldn’t explain the decline in these Bering Sea fur seals. A new study blames pollock trawlers
Fur seals are an essential subsistence food for the Unangax̂ communities in the Bering Sea’s Pribilof Islands. But for years, scientists have been unable to explain why the seals’ populations have been falling.
Now, a new peer-reviewed study points its finger at an industry that’s long been suspected, but never definitively linked with the population declines: Alaska’s huge commercial pollock fishery, which harvests the same species that nursing female seals rely on to feed their pups.
Jeffrey Short is the lead author of a study published in the Journal of Marine Science and Engineering on Sept. 9 which he says presents, for the first time, clear evidence linking the pollock fishery with fur seal reductions.
Some scientists have suspected the pollock fishery, but evidence-based research linking the two has been scarce. According to Short, that’s because much of the existing literature has focused on the overall abundance of pollock, which is quite high.
By contrast, this new study focuses on the pollock catch — that is, the amount of fish being pulled out of the water.
“I was just astonished at how well it worked,” Short said. “Just that single number of pollock catch can explain nearly all of the [fur seal] population trajectory since about the mid-1970s.”
The team found evidence to suggest the pollock industry has made it harder for lactating fur seals to feed their young, by breaking up the dense schools of fish the mothers rely on while fattening their pups.
“What a female lactating fur seal wants to do is [to] find a dense aggregation of food right next to where her pups are,” Short said. “So she can spend the minimum amount of energy to go find it, sit on top of it and eat to her heart's content, and then swim right back and nurse her pups and repeat that all summer long.”
But commercial fishing boats also seek dense schools of fish. By fishing those schools, the fleets break up those dense schools, and the fish disperse. So now, the mother seal doesn’t have that food resource, and she can’t fatten up her pups as quickly as she once could.
That’s a problem because the pups swim south in the fall. If they haven’t built up enough reserves, those seal pups likely won’t survive their first year.
And that, according to this study, is why fur seal populations are declining so steeply.
The number of northern fur seals in the Bering Sea has dropped by around 70% since the 1970s.
“I think it's possible for the fur seal herd to eventually go extinct or become extirpated off the Pribilof Islands,” Short said.
The fur seal rookeries in the Bering Sea hold special importance to the Unangax̂ communities in the Pribilof and Aleutian Islands which rely on fur seals for subsistence.
Martin Stepetin grew up on St. Paul Island — the most populated of the Pribilof Islands — but now lives in Juneau where he advocates for Alaska Native rights.
“We eat those seals, so it gets scary,” Stepetin said. “If you're trying to support your family, and you're trying to put food in the refrigerator, you worry about the future. What about your kids? How much food is there going to be whenever your kids come of age? Are they going to be able to support their families?”
The study suggests that to make any real changes, the fishery — which is one of the most lucrative in the United States — would likely need to limit pollock catch to around a million tons in the areas surrounding the Pribilof Islands. That’s nearly a quarter of the total 1.375 million tons currently allowed.
One pollock industry booster, Stephanie Madsen, said she’s worried about a one-size-fits-all solution.
“It would be devastating to just have a blunt tool. And that’s what I think this 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 paper into the growing body of research on the subject, but she said there needs to be more precise measures than simply limiting the total allowable catch. She also expressed skepticism that limiting catch would improve the seals’ fate.
“When you're talking about drawing circles around rookeries, and preventing fishing from occurring in there, you're making quite a few assumptions about the pollock staying inside that circle, that the fur seals aren't going to go outside the circle,” Madsen said.
The pollock industry employs around 30,000 people nationwide. In the eastern Bering Sea and Gulf of Alaska, the fishery brought in around $420 million in 2020, according to the National Oceanic and Atmospheric Administration.
“Thousands of jobs and tens of thousands of families depend on that income,” Madsen said. “I think depending on the size of those circles, for the most part, it could be quite damaging to the pollock fishery's ability to harvest our quota.”
Madsen said that while she is moderately concerned about the authors’ findings, she doesn’t anticipate they will lead to immediate changes in the industry.
The North Pacific Fishery Management Council, which manages fisheries in the region, receives updates on marine mammals at the beginning 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 get their annual marine mammal updates at their February council meeting.”