Marine mammals on the West Coast may now be eating more Chinook salmon than those being caught by commercial and recreational fisheries combined, a new study finds.
It shows that recovering populations of killer whales, sea lions, and harbor seals have dramatically increased their consumption of Chinook salmon in the last 40 years.
"We have been successful at restoring and improving the population status of protected marine mammals," said Brandon Chasco, a doctoral candidate at Oregon State University and lead author of the study. "But now we have the potential for protected seals and sea lions to be competing with protected killer whales, and all of which consume protected Chinook salmon."
The research was a collaboration of federal, state and tribal scientists in the Pacific Northwest, including Oregon State University and NOAA Fisheries.
"A lot of people in our field know marine mammals are increasing and there's been a lot of concern about predation but it is dramatic when you see the numbers and realize what a major force these predators are in controlling Chinook salmon abundance," said Northwest Fisheries Science Center Director of Conservation Biology Mike Ford. "We need to think about managing this ecosystem in a way that works for both fishermen and these species we care about."
It may have serious implications for the recovery of both Southern Resident killer whales as well as Chinook salmon, both of which are protected by the Endangered Species Act. There are only 76 Southern Resident killer whales alive today, deeply concerning for scientists who believe the orcas may disappear if serious action is not taken immediately.
Southern residents spend much of the year in Puget Sound and the Salish Sea, and their primary diet is Chinook. The study found that the orcas consume about the same volume of salmon today as they did 40 years ago. It suggests that in today's ecosystem, competition with other marine mammals may be more of a problem for southern residents than competition with human fisheries.
The study also shows that several growing populations of resident killer whales in Canada and Southeast Alaska are estimated to consume the largest biomass of Chinook salmon, but harbor seals consume the largest number of individuals, including juveniles which are a main target for habitation restoration efforts around Puget Sound and the Columbia River.
The research found that salmon recovery programs up and down the West Coast have boosted numbers of wild salmon, but increased predation by recovering marine mammals presents a challenge and may offset reductions in recreational and commercial harvests.
"The better we understand the different obstacles to salmon recovery, the better we can account for them as we plan and carry out recovery programs," said Isaac Kaplan, a research fishery biologist at NOAA Fisheries' Northwest Fisheries Science Center and a co-author on the study. "Recovery efforts must account for all of these challenges, and we're providing more details about one important part of that picture."
Pete Knutson owns Seattle-based Loki Fish Company. His family has depended on salmon for decades.
"We've got to start taking concrete steps to restore the ecosystems and the habitat, that's the longterm."
Marine mammals are often seen as competition by salmon fisherman, but Knutson says that anger is misguided.
"They're not stealing my livelihood. The way I look at it, if I put a net out in the water and a seal or sea lion comes and takes a couple of them, that's the tax I'm paying to these folks because that's where they live," he said.
