A judge cleared the way on Thursday for three US.states to kill California Sea Lions caught feasting on endangered salmon while a lawsuit is hashed out in court. But the order by a US District Court judge in Washington DC limits the number of sea lions that can be trapped and killed in three states of the US Pacific Northwest to 30 a year, less than a third of the number the National Marine Fisheries Service would have allowed. The Humane Society of the United States and other animal rights advocates have argued that the sea lions are unfairly blamed for declining fishery stocks on the Columbia River. \"Obviously we are very disappointed that this programme as not halted,\" said Sharon Young, marine issues field director of the Humane Society. \"But, we are grateful that the court put some restraints on it.\" California Sea Lions swim 140 miles from the ocean to gather at the Bonneville Dam dividing Washington and Oregon and prey on endangered and threatened salmon and steelhead trout. The fish collect at the hydroelectric dam as they swim upstream to spawn. Earlier this month, the National Marine Fisheries Service gave the states of Washington, Oregon and Idaho permission to kill up to 92 California Sea Lions per year up to May 2016, but only those known to be eating listed fish and only if they could not be placed in zoos or aquariums. Since 2008, 28 sea lions have been killed and 10 placed in institutions under similar salmon-protection programmes overseen by the Fisheries Service. Federal Judge James Boasberg ordered that no more than 30 sea lions be killed per year and that they may not be shot; only trapped and given lethal injections. The states argue that California Sea Lions are hindering salmon recovery efforts in the Northwest. But animal protection activists say human fishing, hatchery practices, dams and environmental degradation pose a far greater risk to the fish. A lawsuit brought by the Humane Society, the Wild Fish Conservancy and others asks the courts to halt sea lion killings, arguing that the programme violates the Marine Mammal Protection Act and other laws.