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More sea lions at Bonneville buffet

Biologists count 50 already, feasting on salmon far up the Columbia River, much to fishermen's displeasure

04/10/04

MARK LARABEE

 

Californians are invading the Columbia River, and marine biologists are watching with interest.

They're not Bay Area tourists on spring break, but California sea lions feasting on spring chinook in numbers like never before.

It's the third year biologists have been watching the marine mammals gorge themselves on plump salmon -- some of which are endangered -- just below Bonneville Dam. Their aggressive behavior and numbers have some fishermen upset.

In the past, sea lions have been seen at the dam from mid-March through May, said Robert Stansell, a U.S. Army Corps of Engineers biologist. This year they showed up Feb. 26, before large numbers of fish arrived, possibly debunking popular thinking that they were chasing fish runs up the river.

"They knew that in the past they could find fish here," Stansell said, adding that a lot of the sea lions they have counted are repeat visitors. "They're teaching each other. That's a possibility. I don't have any proof of that, but that's certainly my opinion."

Other firsts?

One sea lion jumped into the dam's fish ladder in pursuit of his prey, a problem if others follow, Stansell said. And it's the first year sea lions have been spotted sleeping out of the water near the dam. Usually they eat, hang around in the water for a few days, then leave.

In 2002, the first year of the Bonneville survey, biologists counted 30 sea lions and one harbor seal. Last year, they counted 107 sea lions. So far this year they've counted 50 different animals.

"We're probably going to average more this year," Stansell said.

The greater numbers mean more run-ins with fishermen. Some anglers complained Thursday during a meeting of the Columbia River Compact, a group of biologists from Oregon and Washington who manage the Columbia River fish runs. They said sea lions are becoming so aggressive they sometimes try to get into fishing boats.

Dennis Hull, who owns Salem-based Bite Me Guide Service, was fishing Thursday and hadn't seen a single sea lion, which he said was unusual for this time of year.

"On some days you can watch one sea lion bite the belly out of 20 or 30 salmon," he said. "I think they need to thin them out. They've got too many of them."

Some people may have taken matters into their own hands. Oregon State Police and the National Marine Fisheries Service are investigating whether someone shot a sea lion earlier this month. It's carcass was found a week and a half ago on Sauvie Island apparently dead from a gunshot to the head, said Trooper Luther Schwartz.

Once hunted to fewer than 1,500 on the West coast, sea lions are now protected under the 1972 Marine Mammal Protection Act. Harassing or harming them is a federal crime.

Since protections were put in place, their numbers have swelled to more than 200,000, although there is some preliminary evidence that the population is leveling off, said Bryan Wright, a statistician with the Oregon Department of Fish & Wildlife marine mammal program.

The agency is studying the recent changes in the sea lions' feeding pattern to try to understand what is happening. Wright said the easy answer is that it's natural for sea lions to travel far inland to get to an abundant food source. He said Meriwether Lewis and William Clark made note of large groups of seals and sea lions farther upriver than where Bonneville Dam is today.

"Salmon are bunched up at the dam, and they're easy targets," Wright said. "One mechanism we don't understand is why they're going there in greater numbers."

He said the department is branding sea lions and has attached satellite transmitters to two animals to study their feeding patterns. One with a transmitter has been at Bonneville for two weeks.

"We want to try to understand the frequency of their movements up to Bonneville and when they're not at Bonneville, what are they doing," Wright said.

Officials have tried other ways to limit sea lion killing of salmon. They've used rubber bullets, noise and water bombs to scare sea lions, Stansell said, but nothing worked. They even moved a few away from the dams.

"They were back within a few days," he said. "The only thing that works is hauling them to a zoo."

In the mid-1990s, officials considered killing some "problem" sea lions at Ballard Locks in Seattle that were eating an estimated 65 percent of the winter steelhead but backed off after Sea World agreed to take three of the most ravenous animals. There are no such plans currently.

Stansell said he's not so sure the sea lions are a detriment to the salmon. In 2002, it's estimated that sea lions ate about 1,000 spring chinook at the dam, or about one-third of 1 percent of all the fish passing the dam. Last year it's estimated that sea lions ate 1.13 percent of the chinook.

"They're catching more fish, but is that huge?" Stansell said. "So far it's probably equal to what they traditionally ate, and the old fishermen are unhappy about it."

Mark Larabee: 503-294-7664; marklarabee@news.oregonian.com
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