OLYMPIA –Wildlife managers from Washington and Oregon will resume efforts next week to remove California sea lions that prey on federally protected salmon and steelhead in the Columbia River.
That effort, initiated last year, is intended to protect threatened and endangered fish runs from a growing number of California sea lions. The sea lions feed on spring chinook and steelhead below Bonneville Dam as the fish attempt to navigate the dam’s fish ladders to spawn upriver.
According to the U.S. Army Corps of Engineers, 103 sea lions last year consumed 4,243 salmon and steelhead—the highest number on record—in a quarter-mile area immediately below the dam.
Since January, state and federal biologists have been using underwater firecrackers, rubber buckshot and other non-lethal deterrents to “haze” sea lions away from fish—primarily sturgeon—congregated below the dam.
Next week, wildlife managers will resume removing specific California sea lions under authority granted to Washington, Oregon and Idaho last year by NOAA-Fisheries, the federal agency responsible for managing marine mammals. That authority allows the three states to use lethal or non-lethal means to remove individual California sea lions that have been documented feeding on salmon or steelhead below Bonneville Dam.
Like last year, the states’ first priority will be to place those animals in federally approved zoos and aquariums, said Guy Norman, southwest regional manager for the Washington Department of Fish and Wildlife (WDFW). The states also have the authority to use lethal measures, if necessary, to remove California sea lions that meet the federal criteria.
“As natural-resource managers, we have a responsibility—in instances where a man-made structure has disrupted the natural predator-prey relationship—to do what we can to restore that balance,” said Phil Anderson, WDFW interim director.
“In this case, the prey are fish populations listed for protection under the federal Endangered Species Act, and our response is critical to recovery of these fish populations.”
The removal of specific sea lion predators from the Columbia River will not affect the overall sea lion population, biologists say. California sea lion numbers have grown rapidly since the 1970s and the species is now at “carrying capacity”—near the highest level the environment can sustain—according to wildlife biologists. The U.S. population of California sea lions is estimated at some 300,000 animals, all on the Pacific coast. A population survey conducted in 2006 by WDFW documented 1,200 California sea lions near the mouth of the Columbia River alone.
An interagency Animal Care Committee will oversee the removal operation.
Last year, state wildlife managers relocated six California sea lions to SeaWorld facilities in Orlando, Florida and San Antonio, Texas, where the animals are all reported to be in good health. However, relocation efforts were suspended after six other sea lions died of heat prostration in cage traps. An investigation by NOAA-Fisheries found that the cage doors dropped shut behind the animals while the traps were unattended, but did not determine why the doors closed.
This year, wildlife managers are taking additional precautions to ensure the cage traps function properly, said Robin Brown, marine mammal program leader for the Oregon Department of Fish and Wildlife (ODFW). Under one new protocol, the trap doors will be locked open to prevent them from closing when the traps are unattended, he said. In addition, the doors to the traps have been fitted with magnetic locks that require a code to open.
For more information about sea lion predation at Bonneville Dam, see the WDFW website at http://wdfw.wa.gov/conservation/sealions/.