A California sea lion catches an endangered chinook salmon migrating up the Columbia River in this 2007 photo.

Portland, Ore. ? Wildlife officials have tried everything to keep sea lions from eating endangered salmon, dropping bombs that explode under water and firing rubber bullets and bean bags from shotguns and boats. Now they are resorting to issuing death sentences to the most chronic offenders.

A California sea lion last week became the first salmon predator to be euthanized this year under a program that has been denounced by those who say there are far greater dangers to salmon — including the series of hydroelectric dams on the Columbia.

This is the second year of the program, which is administered by wildlife officials in Oregon and Washington and the National Oceanic and Atmospheric Administration.

Last year, 11 sea lions were euthanized. Another four were transferred to zoos or aquariums.

The sea lions represent a massive headache each year as chinook salmon begin arriving at the Bonneville Dam east of Portland, congregating in large numbers as they return from the ocean. Sea lions have become keenly aware that the dam is a great spot to feast on salmon, easy pickings as they wait to go up the dam’s fish ladders.

“They learn. They come up here and know it’s a good place to eat, and sooner or later the salmon are going to arrive,” said Robert Stansell, a fisheries biologist with the U.S. Army Corps of Engineers.

Officials are tracking 63 additional sea lions listed as repeat offenders. They are identified by scars or by numbers that were branded on them by researchers.

Sea lions have gobbled salmon forever. But their numbers have soared in recent years, as has the number of those cruising upriver to dine on salmon at Bonneville Dam. Frustrations peaked, especially among fishermen who have watched sea lions snatch salmon right out of their gill nets.

At least three of the upper Columbia River spring salmon runs that pass through the dam are listed as threatened under the Endangered Species Act, most significantly the spring chinook salmon run.

The sea lions’ growing numbers forced state, federal and tribal agencies to intensify efforts to protect the region’s multibillion-dollar salmon recovery program.

The sea lions are protected by a 1972 federal law, but an amendment leaves open the possibility that some can be captured or killed if the states request it. Oregon and Washington did in 2006 with the support of Indian tribes and sport and commercial fishing groups.

The primary weapon against the sea lions still remains hazing, but even that has limitations.

“The problem is, as soon as the boats go around the corner, they’re right back,” Stansell said. “Some of the animals that have been there a long time don’t even move when they get hit in the back with a rubber bullet. They just keep eating their fish.”