For years, the sea lions lounging at the Bonneville Dam have had easy pickings from salmon waiting to go up fish ladders to upriver spawning grounds.
Over the weekend, the federally protected sea creatures were themselves easy prey for a gunman who shot and killed six of the sea lions as they lay in traps meant to humanely catch them.
The six salmon-gobbling animals appear to have been shot by somebody on the Washington side during the night, said Brian Gorman, a spokesman for the National Marine Fisheries Service.
Fishermen and American Indian tribes have pushed to protect the salmon and remove the sea lions, by lethal force if necessary.
State and federal authorities were investigating the shootings, and the area was being treated as a crime scene by state and federal agencies, said Brian Gorman, a spokesman for the National Marine Fisheries Service.
The shootings came less than two weeks after an appeals court issued a temporary injunction against federal authorities killing the mammals.
Federal agents have been trapping them instead, but trapping will be suspended during the investigation, said Rick Hargrave, a spokesman for the Oregon Department of Fish and Wildlife. The public is not allowed to kill or trap the animals.
Two closed traps each contained the carcasses of two California sea lions and one Steller sea lion, he said.
In the trapping operations, the traps are left open so the sea lions get used to them. When wildlife agents are ready to remove the sea lions, they close the traps.
Gorman said when officers got to the traps below the dam's powerhouses, where the water is rough enough to make getting to there difficult, they found them closed.
"It isn't clear how someone got access to the traps," Gorman said. "Nobody in an official capacity closed the traps."
The carcasses were found Sunday around noon below the Bonneville Dam on the Columbia River on the border of Oregon and Washington. Necropsies were planned for all the animals.
The discovery came one day after three elephant seals were found shot to death at a breeding ground near San Simeon in central California. Investigators will try to determine whether there is any link between the shootings, Gorman said.
Seven California sea lions were trapped on the Columbia starting April 24 after the 9th U.S. Circuit Court of Appeals approved their capture. One died during a medical inspection before transfer to a Sea World park.
The Humane Society of the United States has gone to court to challenge the authorization, with another hearing set for May 8. Until a judge rules, no animals may be legally killed.
"We're really shocked," said Sharon Young, a Humane Society spokeswoman, who learned about the sea lion deaths from a reporter. "We're a nation of laws, and we should expect people to abide by them."