LEWISTON, Idaho (AP) -- The U.S. Army Corps of Engineers has begun using fireworks to scare sea lions away from the fish ladders at Bonneville Dam, as they are preying on spring chinook salmon returning to the river and its tributaries to spawn.
Bonneville Dam is the first of eight dams the fish must pass before reaching the Lewiston area. On average, about 1,500 fish pass the dam this time of year.
For the past several years, there have been up to 30 sea lions below the dam, said Brian Gorman, a spokesman for the fisheries division of the National Oceanic and Atmospheric Administration. But this is the first year lions have entered the ladder.
Since the sea lions are threatening fish protected by the Endangered Species Act, federal officials can use non-lethal methods to scare them from the dam, and if that doesn't work, provisions under the Marine Mammal Protection Act allow the mammals to be killed.
Sea lions in the Lower Columbia River are estimated to be taking 2 percent of the spring chinook run, according to the Northwest Power Planning and Conservation Council, which recently sent a letter to the federal agencies asking for help.
But the sea lions' feast is not responsible for this year's late return of the fish, Gorman said. The run, measured at Bonneville Dam 140 miles from the river's mouth, is at a record low.
"I think the late arrival of the spring chinook run is a confounding factor, but is probably utterly unrelated to the presence of sea lions," Gorman said. "We have had sea lions below the dam and had good runs."
Gorman was leery of using underwater blasts to deter the sea lions, saying "they are pretty determined if they are in pursuit of prey."
The corps has plans to install grates on the ladders to prevent sea lions from getting in, but won't keep salmon out.
In the life cycle of salmon, eggs are hatched in inland streams, sometimes in high mountain creeks. After a few months of growth, the young fish head downstream to the Pacific, where they will live for years before returning inland to spawn and die.
Anglers can start luring salmon on most rivers April 23, the Idaho Fish and Game Commission announced last month. It left open the possibility of a salmon fishing season on the Upper Salmon River, which has not been available for almost 30 years.
The agency reached an agreement with NOAA Fisheries to let anglers catch surplus hatchery summer and spring chinook returning to some hatcheries on the Upper Salmon River, but officials say the plan will only be implemented if adequate numbers of fish return to the hatcheries.