The pinniped dynamics appear to have changed a bit this spring with Steller sea lions an ever-growing presence, though California sea lions remain ever relentless in their pursuit of spawning salmon in the tailrace of the Columbia River's Bonneville Dam, according to preliminary data compiled by U.S. Army Corps of Engineers researchers.
A total of 63 different pinnipeds were counted below the dam on April 16, a new one-day record high since researchers began monitoring sea lion behaviors and eating habits in 2002. That number included 17 Stellers, also a record count over the course of the ongoing study.
In past years the two sea lion species have preyed almost exclusively on different fish stocks, California sea lions on salmon and steelhead and Stellers on white sturgeon. But early results this year show some change.
California sea lions have been observed taking nine sturgeon so far this year, as compared to six total in the previous years of the study, according to a weekly status report prepared by researchers Robert Stansell, Sean Tackley and Karrie Gibbons. Their reports can be found at: http://www.nwd-wc.usace.army.mil/tmt/documents/fish/
"There has been a noticeable increase in the number of observations of Steller sea lions stealing salmon caught by California sea lions as well as what appears to be direct catches themselves, which may account for the slowing of sturgeon taken over the past few weeks," the report says.
The take has slowed, but the preliminary data indicates the sea lions have already nearly doubled last year's record total with sea lions observed dining on 605 sturgeon, including at least 21 fish that were larger than 5 feet long. The report stresses that the data is preliminary and could change after post-season analysis and proofing.
The salmon take is also on pace to break last year's total. Observers tallied 3,859 salmonids being taken by sea lions in 2007, 4.2 percent of the total passing the dam. The sea lions have over the course of the study begun arriving at the dam in midwinter and for the most left the Columbia by the end of May after the upriver spring chinook salmon run has petered out. The chinook run includes Snake River and Upper Columbia stocks that are listed under the Endangered Species Act.
From Jan. 11 through April 20 researchers have seen sea lions consume 1,791 chinook and 258 steelhead, with the peaks of the upriver run likely yet to arrive. Another 541 unidentified fish have been taken below the dam.
Thus far the researchers estimate they have seen 55 different California sea lions at the dam, which is 146 river miles from the Pacific Ocean. They are now the target of a removal effort launched Thursday by the Oregon and Washington departments of fish and wildlife. Animals will be captured and shipped to zoos and aquariums as an attempt to reduce their impact on listed salmon stocks.
Of the California sea lions seen at the dam over the course of the season (58 individuals), 31 are on the list of animals targeted for removal. Each has been seen consuming salmon at the dam and ignored efforts scare them away.
The Stellers, on the other hand, are ESA listed too and thus largely untouchable. For the third year in a row the states and Corps have mounted a hazing effort from the dam and from boats to discourage sea lion predation. But the firing of seal bombs, cracker shells and other scare tactics have been largely unsuccessful.
"They can be chased out of the tailrace area," Stansell said. But they never stray too far from the prime feeding grounds.
"They're getting very comfortable," he said of the Stellers.
A few of the sea lions apparently are slipping past Bonneville, perhaps through its navigation lock when barges are moved up and down the river.
"“There have been several reported sightings, from reliable sources, in the Bonneville Pool, so there are likely one or more sea lions present," said Stuart Ellis, a Columbia River Inter-Tribal Fish Commission fishery biologist.
Tribal fisherman Robert Brigham of the Umatilla Reservation said he spotted a sea lion on Monday near the boat launch at the Cascade Locks in lieu fishing site.
"“It was swimming around, latching onto fish," he said. “Seagulls were eating what was left over.”
And then on Wednesday, Brigham said, a sea lion was photographed "right along our nets."
Brigham said Warm Springs fishermen last week saw a sea lion above Starvation Creek on the Washington side and there have been sightings above Hood River near Stanley Rock.
Information on sea lion presence in Zone 6 will be useful in the ongoing efforts to remove sea lions below Bonneville, Ellis said. Fishermen are being asked to record the date, time and location of sea lions they spot, as well as what the sea lion is doing. Fishermen also are asked to note if the sea lion has distinguishing marks or brands.
"If a sea lion is hauled out, we would like to know where the haul-out site is," Ellis said. "We are also very interested in getting photographs of sea lions."
If sea lions are spotted around the tribal fishing gear, or interfering with tribal fisheries, fishermen may attempt to chase away the sea lion using slingshots, fireworks, other noise makers, rocks, etc.
But under federal law, Ellis said, it is not legal for anyone, including tribal fishermen, to do anything that might injure or kill a sea lion.
If fishermen see a sea lion, they should report it to Ellis at 503-731-1312 or email@example.com, or they can report it to Columbia River Inter-Tribal Fish Enforcement at 800-487-3474.