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Killer Whales Far More Complex Than Many Think by Editorial Board Capital Press, January 9, 2020

A recent University of Washington study about killer whales could offer another clue to the well-being of the southern resident killer whales that live in Puget Sound and the Salish Sea off the coast of Washington state.

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 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.

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 the Puget Sound?

These facts appear to have been left out of the narrative many environmentalists and politicians have been constructing.

Maybe, just maybe, that’s because reality is far more complicated than they think. Or it doesn’t fit their agendas.

An email response to bluefish.org from the Lead Researcher of the Orca Report

Hi Scott,

I appreciate your interest and comments. Regarding hatchery releases of salmon: it is correct that hatchery production of Pacific salmon has remained relatively stable since the 1980s, as shown on your figure, and also that production of hatchery Chinook salmon has declined over that time period, as mentioned in our paper. Chinook salmon hatchery production is only a small fraction of the total salmon release, which is dominated by chum and pinks. Here is a similar plot to yours using North Pacific Anadromous Fish Commission data for Chinook salmon only (see graphic):

Other Pacific salmon may also affect the growth and maturation of Chinook salmon, such that the total number of hatchery salmon in the North Pacific Ocean might be important, as discussed briefly in our paper.

Regarding your comment on CR June Hogs: I totally agree that expanding our data further back in time would be instructive, as would considering the contributions of local extirpations. The disappearance of local populations, especially if more likely for those that reached particularly large sizes, could be a contributing factor that we did not account for in our analysis, primarily due to lack of data. We also acknowledge that there are likely some regional differences in terms of factors that contribute to local trends. I think we have only scratched the surface...

Thanks for sharing your thoughts and happy new year!

Jan

Jan Ohlberger
Research Scientist
School of Aquatic and Fishery Sciences
University of Washington