New study says decrease in salmon threatens killer whales

Orca whales

BELLINGHAM, Wash. (AP) — Southern Resident killer whales have not had enough food for several years, which could affect their already small numbers.

That’s according to a study by the University of British Columbia.

Researchers looked at the availability of prey for Northeastern Pacific Southern Resident killer whales.

The study found a fluctuating level of salmon from spawning areas on rivers had a detrimental effect on killer whale health, threatening a small and fragile group of whales.

About 75 of the Southern Resident killer whales span from the California coast to British Columbia’s Queen Charlotte Islands. But a decrease in salmon threatens that population.

“With the southern resident population at such a low level, there’s a sense of urgency to this kind of research,” Fanny Couture, a doctoral student at the Institute for the Oceans and Fisheries (IOF) and Ocean Wise, said in a statement. “Both killer whales and Chinook salmon, the southern resident’s main prey, are important, iconic species for the west coast of Canada. Studying what is happening to the population may help offer solutions, both for the southern residents and potentially other killer whale populations in the future.”

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Here is more from the University of British Columbia:

The southern resident population, which feeds mainly on Chinook salmon, numbered 73 individuals as of October 2021, compared with the increasing northern resident population of about 300. Studies have posited that the growth of the southern resident population may be impeded by a lack of food.

The researchers analyzed how changes in the abundance, age and size of Chinook, coho and chum populations that the southern residents prey on in the Salish Sea and at the west coast of Vancouver Island influenced the daily food consumption of the killer whales, from 1979 to 2020 for three seasons each year.

The study used estimated declines in Chinook salmon abundance and size to show that lower availability of these fish has likely resulted in killer whale energy deficits. “The years where southern residents were in an energy deficit are also years where other studies report lower population growth rate and higher mortality rates for the killer whales,“ says co-author Dr. Villy Christensen, professor at IOF.

The Associated Press contributed to this report.


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