Old Fish Face a New Threat: Hungry Sea Lions
January 15, 2008 - The News Tribune
By Susan Gordon
A prized population of Columbia River sturgeon is the latest victim in a familiar Pacific Northwest plot: hungry sea lions exploit a manmade 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, 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. (Federal regulators are expected to decide in March whether to allow government agents to kill California sea lions which target protected salmon.)
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, who have not 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. Many of the sturgeon have been far larger than those fishermen are permitted to catch.
The sturgeon death count began in 2005, James said, when wildlife officers saw sea lions snatch about 60 adult sturgeon downstream from Bonneville dam. Last year, sea lions bit into more than 350, officials said.
Under current rules, commercial and sports anglers are permitted to catch about 40,000 sturgeon annually.
But now, in part because of the seal lion threat, experts said tighter regulation might be needed to protect future generations of sturgeon.
“Our big concern is what’s happening with the brood sturgeon. That’s our whole future we’re gambling with,” said Liz Hamilton, executive director of the Northwest Sportfishing Industry Association, a trade group representing fishing guides, among others. “I’m not going to dispute the fact that Stellers need protection, also.”
Like people, sturgeon take years to mature, and typically don’t begin to reproduce until they are 15 or 20 years old.
Also, sturgeon don’t spawn every year. But when they do, they disperse millions of roe, or eggs.
“It doesn’t take a large increase in mortality to start driving the population down because they do grow so slowly and reproduce so infrequently,” said Dan Erickson, a Pew Institute for Ocean Science biologist who studies sturgeon worldwide.
Biologists aren’t sure why Steller sea lions, who 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 only had 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.
In the 1990s, he said Steller sea lions rarely were seen upriver of Ilwaco, the port at the river’s mouth, which is more than 140 miles downstream of the Bonneville dam. California sea lions went farther upstream to where the Lewis and Cowlitz rivers spilled into the Columbia, he said.
But in the last five years, that’s changed as both sea lion species have gravitated to the dam.
“They’ve got this uncanny ability to find these places where prey are concentrated,” Jeffries said.
The current conflicts at Bonneville between sea lions and salmon and sea lions and sturgeon echo what went on at Seattle’s Ballard Locks starting in the late 1970s and periodically for about 20 years. There, the story was sea lions versus steelhead. By the time it was over, the steelhead run had collapsed.
At Bonneville, as at Ballard, manmade 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 has made them easy prey for Steller sea lions, said Jeffries. “It’s like free money,” he said.
Otherwise, mature sturgeon don’t usually fall victim to predators. California sea lions, smaller than Stellers, don’t hassle sturgeon, wildlife officials said. “When you get to be an 8-, 9-, or 10-foot-long fish, not too many things bother you,” Parker said.
Biologists haven’t seen a Steller-sturgeon attack because they occur under water. 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.
For male sea lions, the goal is to maximize caloric input, Jeffries said. Instinctively, the Stellers seek to bulk up and dominate their territory. “The bigger you are, the badder you are,” Jeffries said.
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.
Susan Gordon: 253-597-8756; firstname.lastname@example.org
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