Dwindling fish supply stresses endangered killer whales
Source: Lynda V. Mapes, The Seattle Times
SEATTLE -- Lack of food - not noise from whale-watching boats - is most stressful to Puget Sound's endangered killer whales, researchers have learned.
Levels of certain stress hormones decreased in samples of orca scat gathered during the time of highest vessel traffic, instead of increasing, researchers found. They surmise this is because at the same time, the whales' favorite food, chinook salmon, was most abundant.
Interestingly, the orcas' stress-hormone levels only increased when vessel noise was higher if there also were lower levels of food available at that time.
"I like to call it my buffet-in-a-bar example," said Katherine Ayres, lead author of a paper on the study published in PLoS ONE, released Wednesday. Patrons in a noisy bar won't mind the racket if all their favorite foods are piled high on the buffet. "But you go there and they are only serving rice and potatoes, and it's super noisy and crowded, then it's, 'I am not getting a good meal and these boats are driving me crazy.'"
Sam Wasser, director of University of Washington's Department of Biology Center for Conservation Biology, said the study points to the importance of putting fish first as managers look for the priority management steps, amid reducing toxins and pollution, vessel noise and improving food supply, for orca recovery.
"If you are a manager, you really want to know what are the relative importance of those, and how do they interact, and our study did that; it found that fish are the most important," Wasser said.
Efforts to build up Puget Sound chinook have been under way since before they were listed as threatened more than 10 years ago.
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