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NW Fishletter #272, March 17, 2010

[5] Six Sea Lions Euthanized At Bonneville Dam

The Corps of Engineers has reported that six California sea lions have been euthanized so far this year at Bonneville Dam. Most were trapped on Mar. 9, along with two Steller sea lions, who were released. Four traps have been placed near the corner collector at Bonneville Dam.

Observers have tallied more than 900 sturgeon caught by Steller sea lions, and 130 steelhead eaten by California sea lions. So far, only one chinook salmon has been seen to be eaten by a sea lion, but the spring run hasn't yet materialized.

The Corps' latest report says up to 31 Stellers have been seen at the dam, along with a dozen California sea lions. At least 10 of the sea lions have been seen before and are on the list for removal.

The Corps said they have not found any facilities willing to take any captured mammals off their hands. Last year, after some trapped California sea lions passed physical exams, they were placed at several aquariums around the country. But others were not so lucky.

Twenty sea lions were captured last year, six were branded or tagged and released, four were removed to aquariums and 10 were euthanized after it was determined they carried diseases that made them undesirable for relocation.

Readily admitting to using many assumptions in its analysis, a Corps' report from last November estimated that the 25 sea lions removed over the past two years has allowed a thousand or more extra spring chinook to pass the dam. That's only about .3 percent of the 297,000 spring chinook adults counted passing the dam in 2008 and 2009.

This year, nearly 500,000 spring chinook are expected to show. Last year, the marine mammals near the dam were estimated to have consumed nearly 3 percent of the run. But another thousand or so sea lions hang out in the lower Columbia and they may be eating 20,000 chinook every spring, a NMFS official said last year. -B. R.

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