GRANTS PASS — Oregon officials were successful in getting permission to kill sea lions that feed on protected salmon trying to swim upriver to spawn. Now they want federal approval to shoot a type of seabird that eats millions of baby salmon trying to reach the ocean.

In an April 5 letter to the U.S. Fish and Wildlife Service, Oregon Wildlife Chief Ron Anglin said harassment has “proved insufficient” in controlling double-crested cormorants. He said officials want the option of killing some of the birds to protect endangered wild fish as well as hatchery fish vital to sports and commercial fishing.

Oregon needs federal approval to start shooting dozens of the long-necked, dark gray seabirds on coastal rivers because they are protected under the Migratory Bird Treaty Act.

The letter obtained by The Associated Press was a formal request to add Oregon to the 28 states authorized to kill cormorants to protect public resources, such as game fish. The Fish and Wildlife Service is updating the authorization, which expires in 2014.

Anglin said sportsmen’s groups have been pressing the agency for years to do something about the growing numbers of cormorants, and research on the millions of salmon being eaten by the big nesting colony at the mouth of the Columbia River brought the issue to a head.

Once considered a nuisance bird, cormorants were added to the Migratory Bird Treaty Act in 1972, the same year the pesticide DDT was banned.

Current estimates are that about 70,000 cormorants live in the West between southern British Columbia, the Mexico border and the Continental Divide, said Dan Roby, a professor of wildlife ecology at Oregon State University who is studying the birds.

The largest nesting colony in the West is now on East Sand Island, at the mouth of the Columbia, where more than 27,000 birds are blamed for eating 22.6 million young salmon last year, 15 percent of the smolts — hatchery and wild — heading to the ocean, Roby said.

The U.S. Army Corps of Engineers is just starting work on a plan to deal with the birds.