Sea lions feast on sturgeon at Bonneville Dam

Posted: Sunday, February 27, 2011

BONNEVILLE, Ore. — Lenza Paul and Michael Farber stand at the lip of Bonneville Dam, layered against the winter cold, binoculars and clipboard in hand, and count.

On 29 weekdays from Jan. 7 through Feb. 17, Steller sea lions killed 1,400 sturgeon, already surpassing last year’s total.

For 10 years the highly publicized fight on the Columbia River and in the courts has been over California sea lions that show up below Bonneville Dam in March to eat endangered, migrating spring chinook salmon. A few years ago, the Stellers came to the feast. Some are staying year-round, having discovered the thousands of slow-moving, white sturgeon clustered below the dam to grow and breed.

The Stellers have come to the table just as sturgeon numbers are crashing.

A sharp decline in the last four years in juvenile sturgeon as well as older breeding fish in the Columbia has biologists both puzzled and looking for solutions.

Oregon and Washington fishery agencies petitioned to remove Steller sea lions from federal protection — it is listed as “threatened” under the Endangered Species Act. Key to that is to count how many salmon, steelhead and sturgeon the Stellers take.

The decline led Oregon and Washington this month to put the tightest limits ever on sport and commercial sturgeon fishing, the fourth straight year of cuts. While the states are about to adopt a conservation plan, most biologists and fishermen fear a continued decline of sturgeon, and an eventual halt to all sport and commercial fishing.

“Stellers are larger, they’re adaptive, they’re predators, they’re smart,” says Robert Stansell, the U.S. Army Corps of Engineers fish biologist who has run the Bonneville Dam sea lion predation counts since they started in 2002. “They know how to prey on fish and they’ve learned there’s a huge sturgeon population here.”

The corps estimates that California and the threatened Steller sea lions took 4,000 to 6,000 migrating spring chinook each of the past three springs as they cluster below Bonneville Dam to enter the fish ladders.

The Marine Mammal Protection Act restricts what humans can do to California sea lions, even though they aren’t listed as threatened or endangered. In 2006 Oregon and Washington got federal permission to haze them and a year later permission to remove or kill up to 85 a year. Over the next three years agencies captured and moved 10 California sea lions to aquariums, and euthanized 30 others. The most California sea lions spotted at Bonneville was 104 in 2003; 89 were observed last year.

The first California sea lions of 2011 were observed Monday at Bonneville — the latest appearance in five years. California sea lions mainly feed on salmon and leave in June when the spring run ends.

Stellers, on the other hand, stay below the dam all year now, Stansell says, and clearly have developed a taste for sturgeon. Already this year, 32 different Steller sea lions have been counted below the dam. Larger — they weigh 2,000 pounds — and more aggressive than California sea lions, the Stellers are pushing their way in. Only a handful were observed each year from 2002 through 2007; the number jumped to 39 in 2008, then to 75 last year, according to the corps’ counts.

Stellers eat sturgeon until salmon runs begin in March then return to sturgeon once the salmon move upriver. And the fish are easy pickings: While spring chinook travel fast to reach the upper Columbia, sturgeon are the opposite — they can’t climb the fish ladders and the larger breeding fish prefer the turbulent water below the dam to spawn.

Oregon, Washington and Alaska last year petitioned to take Stellers from Alaska to California off the federal threatened list, arguing that overall increases met 3 percent growth for 30 years. The National Marine Fisheries Service has said delisting “may be warranted” and a decision is due in August. Even then, though, state fishery managers could get permission to remove or kill Stellers only if they are hurting an endangered species — and sturgeon are not.

Guy Norman, a Washington Department of Fish & Wildlife regional director, says it may come down to asking Congress to change the Marine Mammal Protection Act to include sturgeon.

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