Competition For Chinook By Seals, Sea Lions Limiting Salish Sea Orca Recovery, Study Says

Despite decreasing Chinook catches over recent decades, runs haven’t increased overall and more new research is pointing the finger at the bellies of growing West Coast marine mammal populations, a hunger that may be “masking” salmon recovery efforts.

A study out today says that between 1975 and 2015, sea lion, harbor seal and killer whale appetites for the nutrient-rich salmon more than doubled, growing from 6,100 metric tons annually to 15,200 metric tons, or 33,510,264 pounds.


That’s the equivalent of 31.5 million kings, up from 5 million 40 years ago.


The study was published by researchers from Oregon State University, NOAA’s Northwest Fisheries Science Center and WDFW and tribal biologists, among others, in the journal Physical Reports under the headline “Competing tradeoffs between increasing marine mammal predation and fisheries harvest of Chinook salmon.”

The rub is that the fish and finned mammals are both protected by federal laws.

While killer whales account for the lion’s share of Chinook poundage consumed — especially those packs that haunt the waters from the west coast of Vancouver Island north to the Gulf of Alaska — the study suggests that the increasing numbers of pinnipeds are impacting the ability of Puget Sound’s orcas to recover more so than our fishing seasons targeting kings.

“Our results suggest that at least in recent years competition with other marine mammals is a more important factor limiting the growth of this endangered population than competition with human fisheries,” researchers state.

Pinnipeds are infamous for stealing Chinook off anglers’ lines, but much of what they eat are actually juvenile fish — harbor seals in particular.

Those in the Salish Sea, which includes Puget Sound and the Straits of Juan de Fuca and Georgia, consume 86.4 percent of all those smolts eaten by marine mammals, “due to large increases in the harbor seal abundance in this region between 1975 and 2015 (8,600 to 77,800).”

“For Salish Sea Chinook salmon, strong increases in predation greatly exceed harvest; this is driven largely by local increases in pinniped abundance in the Salish Sea,” researchers write.

Overall, West Coast recreational and commercial catches have declined from 3.6 million to 2.1 million kings, while marine mammal consumption of adult salmon has risen from 1.3 million to 3.1 million.

Hatchery production peaked around 1985 at 350 million but has since declined to around 225 million a year. Overall hatchery and wild production is running between 400 million and 475 million in recent years, according to the study.

“… (L)ong term reductions in the salmon available for commercial and recreational fisheries may not reflect lower abundance of salmon, but rather a reallocation from human harvest to marine mammal consumption,” the authors write. “Because many populations of Chinook salmon in the Northeast Pacific are of conservation concern, substantial resources have been invested to improve salmon passage through hydropower dams, restore salmon habitat, reduce fishing, and otherwise improve conditions in rivers and streams to improve productivity. Collectively, these recovery efforts may have increased Chinook salmon survival or recovery, but these increases in salmon populations may be offset by salmon consumption by more-rapidly increasing populations of marine mammals and other predators.”

Columbia Basin fishery managers and others are pushing to increase lethal removals of sea lions, including most recently at Willamette Falls.

The new study, which looks at ocean impacts, found that for Chinook stocks from the Columbia south, “predation impacts have increased strongly over time and exceeded harvest in recent years.”

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