BONNEVILLE DAM, Ore. – Sea lions making a nuisance of themselves by indulging in a fish ladder feast at Bonneville Dam may find their dining interrupted soon.
They may face bombardment with noisy fireworks, high-pressure water hoses and irritating sounds broadcast underwater as biologists try to keep them from damaging fish runs.
Until recently, the marine mammals had not climbed the fish ladders. But one sea lion this year has made repeated runs up and down both of the fishways, eating a steelhead or two in front of visitors and the workers who count salmon.
The new behavior presents a significant problem because the presence of sea lions within the narrow fish passageways could deter large numbers of salmon from entering and heading upstream to spawning grounds.
The Army Corps of Engineers, which operates the dam, met Friday with state and federal wildlife officials to decide how to stop the incursions.
They hope to install equipment next week to broadcast high-pitched sounds underwater, a tactic that worked at Ballard Locks in the Puget Sound when sea lions were killing as much as 65 percent of the winter steelhead in the mid-1990s. But that was only after authorities captured three of the leading offenders and shipped them to Florida’s Sea World.
Robert Willis, environmental resources branch chief for the corps, said biologists hope the hazing will unnerve the sea lions at Bonneville because the animals have not become as tame as the Ballard Locks trio.
“They are relatively inexperienced,” Willis said.
Workers at the dam are also being equipped with “screamers” and “poppers” – noise-making fireworks to shoot above and below water when sea lions approach or enter the fish ladders. The agency also will set up a high-pressure hose to shoot at sea lions, which biologists at the meeting Friday said is forceful but unlikely to injure the animals.