Scientists ID another possible threat to orcas: pink salmon

Gene Johnson, Associated Press
Updated 5:08 pm CST, Friday, January 18, 2019

SEATTLE (AP) — Over the years, scientists have identified dams, pollution and vessel noise as causes of the troubling decline of the Pacific Northwest's resident killer whales. Now, they may have found a new and more surprising culprit: pink salmon.

Four salmon researchers were perusing data on the website of the Center for Whale Research, which studies the orcas, several months ago when they noticed a startling trend: that for the past two decades, significantly more of the whales have died in even-numbered years than in odd years.

In a newly published paper, they speculate that the pattern is related to pink salmon, which return to the Salish Sea between Washington state and Canada in enormous numbers every other year — though they're not sure how. They suspect that the huge runs of pink salmon, which have boomed under conservation efforts and changes in ocean conditions in the past two decades, might interfere with the whales' ability to hunt their preferred prey, Chinook salmon.

Given the dire plight of the orcas, which officials say are on the brink of extinction, the researchers decided to publicize their discovery without waiting to investigate its causes.

More:
https://www.chron.com/news/us/article/Scientists-ID-another-possible-threat-to-orcas-13545532.php