Sea Lions Cut Back on Spring Salmon
By ERIK ROBINSON
A sea lion hitches a ride aboard a barge transiting the lock at Bonneville Dam earlier this year. Observers with the Army Corps of Engineers estimate sea lions devoured about 2.8 percent of this year’s spring salmon migration.
Sea lions consumed a smaller proportion of the spring salmon run at Bonneville Dam this year, but federal authorities figure human intervention had little to do with it.
The pinnipeds have in recent years congregated 145 miles up the Columbia River, where they can target spring salmon at the man-made bottleneck created by Bonneville. State fisheries managers aborted a trap-and-relocate proposal early last month, after six dead sea lions were discovered in a pair of side-by-side traps.
The Army Corps of Engineers, which operates the dam, observed 4,230 salmon and steelhead eaten by almost 100 sea lions. That’s about 2.8 percent of the total arriving at the dam – less than the 4 percent consumption rate of recent years.
The proportional decrease is nothing to be enthused about, said Robert Stansell, a fisheries biologist for the corps.
Stansell said the proportion was smaller because this year’s overall run happened to be greater than in some past years; the total number of fish eaten is roughly the same.
“They’re not reducing the number of fish being taken,” he said. “They take their quota no matter what.”
Observers at the dam calculated sea lion predation between Jan. 1 and May 31, with most of the sea lions arriving with the bulk of the salmon run in early April through mid-May.
The situation creates a conflict between wild salmon protected by the Endangered Species Act and sea lions covered by the Marine Mammal Protection Act.
Brian Gorman, a spokesman for the National Marine Fisheries Service, which last year granted state fishery managers a waiver so they could kill nuisance sea lions at the dam, said the actual number of salmon eaten at the dam is certainly higher than the number seen by observers.
“Clearly, there’s predation that takes place underwater and some at night,” Gorman said.
The Humane Society of the United States successfully blocked the state’s lethal-removal program this year with a lawsuit. Among the organization’s arguments, it contends that the lethal-take permit can’t possibly meet the law’s “significant adverse effect” threshold when state fishery managers allow human fishermen to incidentally kill as much as 12 percent of imperiled wild fish.
Meanwhile, federal investigators revealed no new information about the deaths of the four California sea lions and two Steller sea lions in the traps, saying the investigation remains open.
The animals were discovered shortly before noon on Sunday, May 4.
Officials initially supposed that the animals were killed by gunshots. They backed off that assertion and subsequently indicated the deaths were consistent with heat stroke, although temperatures at the time were mild. It remains unclear how two trap doors on the pair of side-by-side floating traps were triggered, trapping three sea lions in each cage.7
Originally published by ERIK ROBINSON Columbian staff writer.
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