(CN) - Animal-rights groups urged the 9th Circuit on Friday to halt a plan to trap and kill California sea lions that feed on protected fish species near the Bonneville Dam, asking the court, "When does it end? When does the killing stop?"
Ralph Henry, a lawyer with the Humane Society of the United States, said the National Marine Fisheries Service (NMFS) had invoked a "narrow exception to kill sea lions," but could not point to the specific conditions needed for it to end.
This is the second time the issue has been raised in the 9th Circuit; the same three judges on Friday's panel vacated a similar federal authorization three years ago.
Oregon, Washington and Idaho first asked the NMFS in 2006 for permission to "take" California sea lions that eat salmon and steelhead just below the dam, which acts as a bottleneck to fish migrating upstream in the Columbia River.
The request was part of an effort to protect threatened or endangered populations of salmon and steelhead.
But California sea lions are also protected. The Marine Mammals Protection Act bans the taking of all marine mammals, unless individual animals "are having a significant impact on the decline or recovery" of threatened or endangered species.
Another species of sea lion, the Steller sea lion, also feeds at the dam but is off limits because it's protected by both the Marine Mammals Protection Act and the Endangered Species Act.
In 2008 the states were permitted to kill up to 85 California sea lions per year, but the 9th Circuit vacated that authorization in 2010. The federal appeals court said NMFS failed to explain why sea lions posed a greater threat to endangered fish than commercial fisheries and hydroelectric power plants.
The agency had authorized fisheries to take up to 17 percent of the dam's protected fish, yet determined that the maximum 4.2 percent of fish killed by sea lions, according to the Army Corps of Engineers, had a "significant negative impact" on the species.
After the ruling, the states resubmitted their applications, and the NMFS issued new letters of authorization in 2011 after a shortened review process. This triggered another lawsuit, prompting the agency to cancel the new authorizations.
In March 2012 the agency granted yet another round of authorizations, this time to kill or permanently capture up to 92 California sea lions per year. The authorizations are good until June 2016, and allow the states to trap and euthanize individual animals or to shoot them under certain conditions.
The Humane Society, along with the Wild Fish Conservancy, filed a new lawsuit under the Administrative Procedures Act, the Endangered Species Act and the Marine Mammals Protection Act. They claim NMFS simply recycled its analysis to support the kill authorizations without addressing the problems raised by the 9th Circuit.