PORTLAND — Indian tribes are pressuring state agencies in Washington and Oregon for authority to kill protected sea lions that are feasting on salmon in the Columbia River near Bonneville Dam.

The request from the tribes comes as wildlife managers try to comply with federal laws that protect both salmon and sea lions while fulfilling treaty obligations that ensure tribal-fishing rights.

A dozen stocks of salmon and steelhead are listed as threatened or endangered in the Columbia Basin.

But the Marine Mammal Protection Act of 1972 makes it a federal crime to harass, injure or kill California sea lions, which flock to the Columbia River in spring to devour migrating swarms of chinook salmon and other fish, such as smelt.

Sea lions have fished for spring chinook below Bonneville Dam almost every year since the 1980s. But they have commanded widespread attention this year when, for the first time, the animals invaded the fish ladders at Bonneville Dam.

During the past two years, numbers at the big dam have surged to more than 100 sea lions, and salmon kills have risen sharply.

Spring salmon runs include two wild populations federally listed as threatened or endangered. The sea lions feeding at the fish ladders have raised concerns that they could reduce the number of salmon trying to move upriver to spawning grounds.

Biologists with the Army Corps of Engineers estimated last year that sea lions ate about 4,000 chinook salmon passing the dam, about 2 percent of the upriver run. Large numbers of sea lions and harbor seals also ply the mouth of the river and boldly take salmon from fishing nets and lines.

In a letter sent Thursday to fish and wildlife directors of the two states, four tribes assert that the sea-lion problem "must be quickly addressed or it will quickly escalate."

Charles Hudson, a spokesman for the Columbia River Inter-Tribal Fish Commission, said that although sea lions are protected, the law gives states an option not available to tribes: a process for gaining permission to trap or kill individual seals or sea lions that can be proven to be damaging.

"We are just asking the states to use the authority available to them," Hudson said.

Tribal officials don't expect states to gain permission this year, Hudson said. But they are pressing for action now so that the state agencies will be prepared to kill the most-damaging individual sea lions during the spring chinook run next year, if necessary.

Guy Norman, Washington Department of Fish and Wildlife regional director, said his agency still was considering the need for trapping sea lions at the dam or killing them and may seek federal permission "to keep our options open."