Voracious sea lions threaten sturgeon

A prized population of Columbia River sturgeon is the latest victim in a familiar Pacific Northwest plot: Hungry sea lions exploit an artificial fish barrier, eat their fill of fish and defy wildlife officers to scare them away.

The stage is the Columbia Gorge, downstream of Bonneville Dam, about 40 miles east of Portland, Ore., the first in a series of hydroelectric generators that bottle up endangered salmon and other species.

This time, Steller sea lions, the biggest members of the eared seal family and themselves threatened with extinction, dine on some of the largest and oldest freshwater fish in North America.

The prey are vulnerable matriarchs of a sturgeon population said to be among the world's healthiest. Elsewhere, most sturgeon are extinct or nearly so. They have fallen victim to overfishing, poaching -- think beluga caviar -- and habitat destruction.

Yet white sturgeon below Bonneville persist -- at least until now.

"Predation has suddenly put this in jeopardy," said Brad James, a Washington State Department of Fish and Wildlife biologist. "If nothing's done, the overall population will definitely suffer."

In this case, the villains are perhaps 10 male Steller sea lions, protected by the federal Endangered Species Act and weighing up to 2,400 pounds.

They're bigger than their California cousins, who show up later in the year in pursuit of dwindling runs of spring chinook salmon - and have been targeted for execution because of it.

As with the salmon, Washington and Oregon fish and wildlife officers have intervened. To scare away the sea lions, they drive fast boats, set off underwater noise bombs, and shoot rubber bullets or shotguns loaded with firecracker shells. Unlike the California sea lions, which haven't been deterred, Stellers typically shy away from the noise.

Historically, white sturgeon grew to 20 feet long and lived as many as 100 years. In the 1890s, excessive fishing nearly destroyed the Columbia River population.

Beginning in about 1950, fishery managers realized the importance of mature fish and set size limits to protect them from fishermen. It wasn't until decades later that the sturgeon population below Bonneville recovered.

But the appetites of the Steller sea lions could set the clock back, experts said.

"It's like going into a forest and cutting a bunch of old trees. They don't grow back next week," said Blaine Parker, a sturgeon biologist for the Columbia River Inter-Tribal Fish Commission, which works for several American Indian tribes. "These fish are essentially the anchor for the entire species on the west coast of North America."

The problem is that sea lions have tracked the sturgeon to their spawning grounds, where the mammals feast on the mother lode: mature females, each loaded with millions of eggs.

How many sturgeon have sea lions eaten? Nobody really knows, but fisheries managers estimate hundreds.

Biologists aren't sure why Steller sea lions, which are opportunistic feeders, have targeted sturgeon.

But Charlie Corrarino, an Oregon Department of Fish and Wildlife conservation manager, said the big fish are about the only ones in the river right now.

Smelt, an important forage fish, have nearly disappeared, noted Parker, the Inter-Tribal Fish Commission biologist. Tons of the thin, oily fish used to flood the lower Columbia and its tributaries in winter. Sea lions had only to open their mouths, let the smelt swim in, and then swallow, he said.

The presence of sea lions so far upriver "is a relatively new phenomenon," said Steve Jeffries, a Washington Department of Fish and Wildlife marine mammal expert.

"They've got this uncanny ability to find these places where prey are concentrated," Jeffries said.

At Bonneville artificial structures restrict fish passage, so migrating salmon and steelhead stack up below the dam. The sturgeon that return to the river to spawn cannot bypass the structure. That's made them easy prey for Steller sea lions, said Jeffries.

"It's like free money," he said.

Biologists haven't seen a Steller-sturgeon attack because they occur underwater. But Jeffries said he believes the sea lions have figured out how to get around the sturgeon's protective armor, or scutes.

Somehow, he said, Stellers manage to lift sturgeon off the river bottom, bite into the bellies, which lack armor, and eat the eggs.

This winter, the two-state wildlife department effort to protect the sturgeon began in December, a couple of months earlier than last year.

It's too early to say whether the scare tactics will prove worthwhile, said Corrarino, the Oregon conservation manager.

This year, instead of attacking alone, the Stellers appear to work in packs.

"They're very, very, very effective," he said.

E-mail Susan Gordon at susan.Gordon(at)thenewstribune.com

(Distributed by Scripps Howard News Service, www.scrippsnews.com.)