Removals of salmon-eating California sea lions resumed this week when two of the big marine mammals were the captured below the Columbia River’s Bonneville Dam by state officials and chemically euthanized.

So far, few salmon, and even fewer California sea lions, have shown up at the dam. The “upriver” spring chinook count this year at Bonneville through Wednesday totaled 49 adult salmon, according to data posted online by the U.S. Army Corps of Engineers, which operates the dam. The counts at the dam usually rise to a peak in late April or early May.

At most eight individual California sea lions have been seen at Bonneville on any one day this year. And overall 11 different CSLs have been seen at the dam so far this season, which is a bit behind past years’ totals for this point in time, said Corps researcher Robert Stansell. During the past 10 years as many as 104 of the big pinnipeds have been seen at the dam over the course of a season, though the number was about half that last year. Most of the sea lions have exited the river by the end of May.

Personnel from Oregon and Washington departments of fish and wildlife are operating four floating sea lion traps at Bonneville Dam at various locations across the season. Traps were used to brand and/or put acoustic and/or GPS tags on sea lions. Observers atop the dam chart the eating habits of identifiable sea lions below the dam.

Researchers have estimated that the pinnipeds take from 1.5 to 4 percent of the spring chinook salmon run in the waters immediately below the dam, which is located 146 river miles from the Pacific.

The states of Idaho, Oregon and Washington have sought authority under the Marine Mammal Protection Act to remove individually identifiable California sea lions that are known to have a significant impact on salmon and steelhead stocks that are listed under the Endangered Species Act.

NOAA Fisheries Service first granted such authority in March 2008 and the states from 2008-2010 removed a total of 38 pinnipeds. The agency was able to locate homes for 10 of those animals in zoos or aquariums, but the rest met a fatal end.

Late in 2010 the U.S. Court of Appeals for the Ninth Circuit declared NOAA Fisheries authorizing decision illegal, thus precluding trapping in 2011.

The male sea lions wander north to forage following their early summer breeding season off the coast of California and in Mexico. In recent years more of the pinnipeds than did historically have begun wandering inland in late winter and spring to feed on salmon headed upstream to spawn.

The Humane Society of the United States has maintained, now and in related litigation dating back to 2008, that sea lions are natural predators and kill fewer fish than other legal causes of mortality like fishing and the operation of the hydro system.

The latest lawsuit was filed by the HSUS in U.S. District Court March 19. It alleges that a new NOAA Fisheries Service authorization decision, issued March 15, violates the MMPA.

The HSUS sought a temporary restraining to prevent implementation of the removal program this year but was denied March 22. The court did place a limit, 30, on the number of animals that can be removed this year.

The NOAA Fisheries’ letter of authorization would allow the states to remove up to 92 California sea lions per year for up to five years. Such removals would target marine mammals that are known to prey on salmon searching for an upriver passage route at the dam.

For more information see CBB, March 23, 2012, “Judge Denies Stay For Sea Lion Killing; Limits Take To 30, With No Shooting Allowed” http://www.cbbulletin.com/418331.aspx