A recent University of Washington study about killer whales could offer another clue to the wellbeing of the southern resident killer whales that live in Puget Sound and the Pacific Ocean off the coast of Washington state, often near the mouth of the Columbia River.
According to the study, killer whales along the coast of southern and southeast Alaska, British Columbia and Washington eat more than 2.5 million adult Chinook salmon each year.
With the exception of the southern resident population, which is listed as endangered by the federal government, all of the killer whale populations in British Columbia and Alaska are thriving.
According to the study, the reason may be that the other populations of killer whales — more than 300 off the coast of British Columbia and more than 2,300 off Alaska — are eating millions of the biggest and most sought-after adult Chinook salmon as they migrate southward along the Alaska and Canada coast.
“We have two protected species, resident killer whales and Chinook salmon, and we are trying to increase abundances of both — yet they are interacting as predator and prey,” said Jan Ohlberger, a research scientist in the UW School of Aquatic and Fishery Sciences, in a press release accompanying the study.
The interesting thing about the study is it found killer whales are picky eaters. They like their Chinook salmon big — larger than 25 inches.
“Killer whales don’t show a lot of interest in Chinook until they reach a certain size, and then they focus intensely on those individuals,” Ohlberger said.
That means the biggest Chinooks are eaten by killer whales in Alaska and British Columbia before they even reach the Columbia River and Salish Sea.
“It’s pretty clear that Alaska killer whales and northern residents get first shot at (the Chinook) before they head south through a gauntlet of predators, and that’s when the dregs show up in the Salish Sea,” the study’s co-author, Daniel Schindler, a UW professor of aquatic and fishery sciences, told our colleagues at the Vancouver, B.C., Sun.
Consider a couple of other factors about the southern resident population:
• The state reduced the number of Chinook salmon it produced in its Puget Sound hatcheries at the same time the southern resident population began to shrink. Hatchery production peaked at 80 million Chinooks in 1989 and had declined to less than 40 million in recent years. Chinook salmon spend one to five years at sea before returning to spawn, so that lines up with the killer whale population, which peaked at 98 in 1995 and is now 73.
To its credit, the state Legislature last year ordered the state hatcheries to boost production of Chinook, but it will take years before they are large enough to become killer whale food.
• In its second report, the state’s Southern Resident Orca Task Force says the population typically ranged up to 140 killer whales. But left out was the fact that in the 1960s and 1970s 58 killer whales from the southern population were captured or accidentally killed by marine parks, according to the Center for Whale Research. Those factors, combined with the lack of food because other killer whales have the first dibs on the Chinook migrating southward from Alaska, demonstrate the complexity of life for the southern resident population.
Why is this important? Among other things, some folks believe four dams on the Snake River are reducing the Chinook salmon available for the southern resident killer whales to eat. The most recent UW study, however, suggests that factors such as other killer whales may do far more damage.
In light of this study, a fair-minded person may want to reconsider where the real problems lie for the southern population of killer whales. Is it hundreds of miles away at the Snake River dams, or is it the fact that millions of the largest Chinook salmon are being eaten by other killer whales before they return to Puget Sound and the outer coast?
Ensuring the survival of the southern band of orcas requires a smart assessment of the costs and benefits of a wide array of responses. Political realism suggests seeing what results from ramping up hatchery Chinook production before proceeding with a difficult fight with the agriculture industry, electric utilities, waterborne shippers and others who oppose dam removal. Particularly in light of an increasingly pro-business federal judiciary, careful and deliberate strategies are called for.
When outer coastal waters were designated as critical habitat for endangered Puget Sound-based orcas it was obvious we are in an era when killer whales will get a prescribed share of Columbia-Snake Chinook salmon. With this in mind, advocacy for greatly expanded Chinook production throughout our region will be the mechanism most likely to produce the premium salmon that orcas and people both love.