PORTLAND, Oregon (Reuters) - Wildlife activists sued on Monday to stop the killing of sea lions that have been eating endangered Columbia River salmon, seeking a reprieve for the animals a day before three Pacific Northwest states are authorized to begin executing them.
The lawsuit, filed in U.S. District Court in Washington, D.C., follows last week's decision by the National Marine Fisheries Service to sanction the limited killing of California sea lions.
The Humane Society of the United States, Wild Fish Conservancy and two individual plaintiffs are seeking an injunction barring the authorization from taking effect on Tuesday.
The hungry sea lions swim 140 miles upstream and cluster at the Bonneville Dam, on the border between Oregon and Washington state, to eat salmon and steelhead trout as the fish head up the Columbia River to spawn. That is seen by the states as a threat to the recovery of the fish.
But animal rights activists argue that the sea lions are unfairly blamed for low fish stocks and charge that fishing, hatchery practices, hydroelectric dam barriers, and environmental degradation pose a far greater risk.
"Federal law allows the killing of sea lions only in very limited circumstances, when the agency proves they are having a significant negative impact on salmon," Jonathan Lovvorn, Humane Society senior vice president, said in a written statement.
"The National Marine Fisheries Service's decision to kill hundreds of native marine mammals to reduce salmon losses by a couple of percentage points at best, while simultaneously authorizing much larger man-made sources of endangered salmon mortality, is both outrageous and patently illegal."
Brian Gorman, spokesman in the Seattle office of the National Marine Fisheries Service, called the legal challenge "not unexpected."
"Now, it is up to the court to respond," Gorman said.
Wildlife activists have battled the fisheries service in court for several years over the controversial practice of killing sea lions to protect stocks of Columbia River basin Chinook salmon.
The sea lions are guarded under the Marine Mammals Protection Act and the suit charges the fisheries service's order violates those laws.
Under Thursday's order, the states can kill only sea lions known to have eaten salmon and are limited to 92 animals per year.
The sea lions can be killed only if zoos or aquariums don't want them. Since 2008, the states have killed 28 sea lions and 10 have been sent to zoos or aquariums.
The Federal permission was set to run from March 20 to May of 2016.
The Bonneville Dam is the first hydroelectric dam on the Columbia River, which divides Washington and Oregon.
Editing by Dan Whitcomb