Zalophus californianus, a California sea lion.

Fish-slaughter: Sea Lions Guilty, As Charged

Terri Hansen
5/28/12

CASCADE LOCKS, Oregon –- Predatory male sea lions have set up camp at bottlenecked fish ladders at the base of the Bonneville Dam in the mid-Columbia River basin. They’re hanging out to score easy meals of endangered and threatened Chinook salmon and steelhead on their great journey from the Pacific Ocean to the tributaries that spawned them to spawn themselves.

The sea lions have become good at it, too. Current research indicates that 300 to 500 California sea lions (CSLs) are consuming 16 to 20 percent of the returning spring Chinook salmon listed under the Endangered Species Act (ESA).

It’s frustrating to lose these salmon, says Sara Thompson, public information officer for the Columbia River Inter-Tribal Fish Commission. “They’re the cornerstone of Northwest tribal cultures,” Thompson (Grand Ronde), says. “We’re talking about sea lion predation occurring on the entire lower Columbia River.”

Armed with rifles that shoot non-lethal cracker shells and seal bombs at these deceptively innocent-looking long-whiskered marine mammals, CRITFC fish technicians Bobby Begay (Yakama/Navajo), Laurinda Hill (Athabaskan/Din’e), and Agnes Strong (Yakama/Umatilla) traverse the waters below the dam three days a week during the salmon’s upriver migration in a now six-year hazing program that is consistent with policies set by the Marine Mammal Protection Act (MMPA).

It’s hard for the untrained eye to see dark sea lions in the dark choppy waters. Shots are sporadic, fired seemingly at random. But have no doubt; these folks know what they’re doing. Suddenly Hill shouts, “Fish kill!” A lightning fast shot smacks the rubbery backside of an enormous Steller and sends him diving underwater, but not before he’s consumed an entire salmon in a swift gulp.

Today all we see are Steller sea lions (SSL), but their smaller CSL cousins prey on salmon in these waters too. Both species are protected under the MMPA. The SSLs are relative newcomers, but CSLs are documented as taking at least five times more salmon than are harvested on the lower Columbia, according to data developed by CRITFC senior fish scientist Doug Hatch.

Hatch has worked with the tribes for 22 years researching solutions to rebuilding salmon runs, and his data is relied on by state fisheries (PDF: Removing California sea lions on the lower Columbia River). When a salmon vanishes down a sea lion’s gullet, their future smolt vanish, too. And their potential progeny. It’s a situation that’s become direr with each passing year.

Sea lions are part of the pinniped family that includes bears, dogs, raccoons, and weasels. They like the tribes have been here since time immemorial, but the CSL population has grown from 10,000 to nearly 300,000 today, and their learned opportunistic feeding behavior has upset the delicate wildlife balance.

“Salmon not only supply protein to people and animals such as bears and eggs,” Hatch says. “They also transport marine derived nutrients to the inland forests and aquatic ecosystem.” Even so, CRITFC doesn’t begrudge sea lions for making a living, he says. “We just want to give the salmon to have to pass through a gauntlet of sea lions to get to the eight fish ladder entrances at Bonneville Dam.”

Today the craftiest CSLs swim as far as 145 miles from the river’s mouth to the dam, and each animal consumes an average of seven fish a day. They’re reported feeding on Chinook salmon on Oregon’s Willamette River falls as well. Efforts to relocate them have failed.

“The MMPA has done a great job bringing back these sea lion populations,” says Thompson. “Salmon on the other hand have continued to struggle.”

CSLs decimated the winter steelhead run at the Ballard Locks in Seattle in 1994. That was before options for lethal removal, and today that run is extinct. Although conditions differ on the Columbia River, and are confounded by the Steller’s presence, a task force comprised of federal, state, and tribal wildlife managers, and interested parties agreed sea lions were taking such a toll on threatened and endangered fish at the Bonneville Dam it warranted permanent removal of documented problematic animals. Only the Humane Society of the United States (USHS) dissented from the task force.

On March 15 the National Oceanic and Atmospheric Administration National Marine Fisheries Service granted states the lethal right to remove 92 problematic CSLs (PDF: NMFS’ Pinniped-Fishery Interaction Task Force October 24, 2011 Meeting Report). The agency stated their concern about the impact of some CSL on ESA-listed fish, “is why it’s so important that we continue to address the problem” (PDF: NOAA Fisheries Accepts New Seal Lion Removal Application). The Humane Society promptly filed suit to halt the authorized killings, rejected by a district court judge March 22 but who limited the number of animals that could be killed to 30, and further ruled euthanasia had to be by lethal injection.

Hatch says the removal program is likely the only solution to the problem. “Reducing the allowed take to 30 animals per year probably won't affect the outcome of the program.”

CSLs take the majority of salmon and steelhead but their share is slipping to their SSL relatives, a looming catastrophe because while the largest CSL males don’t get much over 1,000 pounds SSL males weigh in at as much as 2,500 pounds. And the number of SSLs hanging out at the dam in late winter and spring, and their consumption rates has increased every year since 2005.

CRITFC is limited to non-lethal hazing but that too keeps the salmon from hurtling towards extinction. “After we haze Stellers back down the river it takes them two to three hours to make it back to the dam. For those fish that are passing through it’s a win,” explains Begay. “Hazing is a success if we can get one, five, ten salmon past the sea lions and the dam,” says Thompson.

Begay says CRITFC’s considerable financial and human investment in salmon recovery is protecting their first foods. “We’re going to rebuild the salmon populations, but it takes all of us working together.”

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