Wildlife officials in Oregon have begun killing California sea lions that are eating too many of a type of vulnerable fish.

Three sea lions were killed last week as part of a conservation effort to protect winter steelheads in the Willamette River, The Associated Press reported Thursday.

A federal permit from the National Marine Fisheries Service allows officials to kill up to 93 California sea lions annually after attempts to trap and relocate the 1,000-pound animals failed.

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The sea lions are eating so many of the fish in the river near Portland, Ore., that the trout are at risk of extinction.

A record-low of 512 wild winter steelhead survived the trek past the Willamette Falls, a grim comparison to the more than 15,000 fish recorded by the state less than 30 years ago.

The trout travel from inland rivers to grow into adult steelheads in the Pacific Ocean before returning to the rivers to spawn, AP noted.

Sea lions breed in Southern California and northern Mexico during the summer before the males head north to the Pacific Coast to forage.

Wildlife officials tried to relocate about a dozen of the dog-faced sea lions last year but the animals just swam back to the falls to catch more steelheads.

Sea lions can be killed if they are observed eating at least one steelhead near Willamette Falls between Nov. 1 and Aug. 15 or been spotted along the same stretch of river for two consecutive days, AP reported.

Bryan Wright, project manager for the Oregon Department of Fish and Wildlife’s marine resources program, told the outlet that the state must notify a zoo or aquarium about the sea lion beforehand. They must hold one for 48 hours before killing it.

The sea lions are euthanized by a veterinarian by lethal injection, the outlet noted.

The animal themselves are endangered after decades of being hunted for their thick full. Their population numbers have increased significantly since the 1972 Marine Mammal Protection Act, jumping from 30,000 in the 1960s to about 300,000 today.