California sea lions haunting the lower Columbia River below Bonneville Dam apparently got the memo.
Within a few days of NOAA Fisheries’ notice that the states of Oregon and Washington would once again be allowed to trap and remove big pinnipeds that are known to prey on salmon, the sea lions began their annual exodus from the river.
“They’re disappearing in droves,” Robert Stansell said early this week. Stansell of the U.S. Army Corps of Engineers heads a research project at the dam aimed at evaluating the impact sea lions have on salmon and steelhead stocks headed upriver to spawn. Those stocks include wild fish that are listed under the Endangered Species Act.
As of Monday only two or three California sea lions remained in the waters below Bonneville. By Thursday a single California sea lion lingered at the dam. As many as 50 different California sea lions have been observed feeding below the dam this spring, as well as 70 individual Stellers.
The male California sea lions swim north in fall, winter and spring in search of food and during the past decade a relatively large number have chosen to swim inland in late winter and spring to feast on, for the most part, upriver spring chinook salmon searching for Bonneville’s fish ladders. The congregation of marine mammals, which includes Steller sea lions, typically has exited the Columbia system by the end of May.
The California sea lions have appointments on their southern California-Mexico breeding grounds in early summer. About 200 California sea lions have been observed at Astoria this week staging for their trip south, Rick Hargrave of the Oregon Department of Fish and Game said.
“I think what they (state biologists) will do is look for opportunity” in the coming days to trap eligible California sea lions at Astoria, Hargrave said. That includes targeting two pinnipeds that have found their way, likely through the locks, above Bonneville Dam, which is located 146 miles from the Pacific Ocean.
“They’ve moved a trap up there,” Hargrave said of the state trapping crew. On Thursday one of the two California sea lions in Bonneville’s forebay was trapped and transferred downriver for release below the dam, Stansell said.
State biologists on Monday trapped four animals, including one Steller that was immediately released. An unmarked California sea lion was branded for future identification purposes and released. Two branded CSLs that were not eligible for removal were trucked to Astoria, “hoping that they would just go south,” Hargrave said.
The states in 2006 sought and in March 2008 received authority from NOAA Fisheries to remove “individually identifiable California sea lions are having a significant negative impact on the decline or recovery of salmonid fishery stocks” which have been ESA listed. That authorization was deemed illegal by a federal appeals court panel that in November 2010 said the federal agency needed to better explain its rationale for protecting salmon by allowing the removal of sea lions.
NOAA Fisheries responded May 13 by issuing a new letter of authorization replete with its expanded explanation of how the sea lions’ sins compare with the causes of similar or greater salmon mortality, such as sport and commercial harvest and the operation of the federal Columbia-Snake hydro system.
“We were hopeful that that would be the decision so we could get back to managing the situation,” said Guy Norman, director of the Washington Department of Fish and Wildlife’s Southwest Region.
The authorization covers removal of up to 85 California sea lions annually, although the agency said it was unlikely that large a number would be taken each year, based on the three years the program has been in effect. A total of 37 animals were removed from below the dam during those three years. The agency's new authorization to the states expires in June 2013, but may be extended.
Conditions of the letter of authorization require that, to be eligible for removal, an identifiable California sea lion must:
-- have been observed eating salmonids at Bonneville Dam, in the "observation area" below the darn, in the fish ladders, or above the dam, between January 1 and May 31 of any year;
-- have been observed at Bonneville Darn on a total of any 5 days (consecutive days, days within a single season, or days over multiple years) between January 1 and May 31 of any year; and
-- are sighted at Bonneville Dam after they have been subjected to active nonlethal deterrence.
“What I heard was that it was 99.9 percent the same as the decision that we had been working under,” Hargrave said of the conditions outlined in the new NOAA Fisheries letter of authorization.
A total of 115 California sea lions, including those that have already been removed and either shipped to zoos or aquariums, euthanized or died in captivity, are on the “list” for removal.
The states are not authorized to remove Steller sea lions, which are protected under the ESA as well as the MMPA.
As of May 11, researchers at the dam had seen a high daily abundance estimate for pinnipeds at Bonneville dam this year of 48 on April 26. They have documented more than 70 different individual Steller sea lions since Jan. 7, including at least 26 confirmed as seen in past years. Also documented through May 11 have been close to 50 individual California sea lions, about 28 of which have been seen in previous years (1 for 8 years, 1 for 7 years, 4 for 4 years, 3 for 3 years, 19 for 2 years).
If that number holds at 50 it would be the fewest California sea lions seen at the dam since 31 were documented in 2002, the first year of the study.
“Total salmonid catch for CSL is going to be much lower than the last few years, but SSL salmonid catch is going to be just under the estimate of last year,” according to a May 13 research status report produced by Stansell’s team. The researchers had through May 11 observed Steller sea lions taking 500 salmon and California sea lions taking 1,338. A total of 176 steelhead have also been taken so far. Last year 3,900 salmonids were taken by sea lions through the end of May.
The observed 2011 sea lion take below the dam through May 11 included 1,353 white sturgeon. The vast majority of the sturgeon take has been be Steller sea lions.
The two California sea lions above the dam have both been seen in Bonneville’s forebay laying on log booms at Powerhouse 1 and swimming around Powerhouse 2. One was seen by researchers at Bonneville last year, the other had been seen briefly below Bonneville this year on just one day.