(AP) -- Killing or removing 25 California sea lions over the past two years has not reduced the toll on salmon at the base of Bonneville Dam in the Columbia River.
A new report from the U.S. Army Corps of Engineers estimates sea lions ate 4,960 salmon and steelhead during the spring of 2009 - 2.4 percent of the fish passing the dam located near Cascade Locks, Ore. That compares to an adjusted estimate of 4,927, or 2.9 percent of the run, in 2008.
And while the number of California sea lions was down - 54 this year compared to 82 in 2008 - the average number of salmon eaten by each one was up, along with the number of Stellar sea lions - 26 this year compared to 17 last year.
Sharon Young of the Humane Society of the United States said the numbers show that trying to restore salmon by killing predators does not work at a place like Bonneville Dam.
"You have to address the root issues causing problems for the salmon," such as the dams, fishing, habitat loss and irrigation withdrawals, she said. "Obviously, if predation were the primary issue in the recovery of salmon, we wouldn't be seeing the run size fluctuating like this. The run size fluctuates due to oceanic variables to which the animals are exposed."
The report showed spring runs steadily increasing from 88,474 in 2007 to 186,060 in 2009, while the numbers of salmon eaten by sea lions stayed about the same - 4,335 in 2007 when no sea lions were removed and 4,960 this year after 25 were trapped and killed or sent to aquariums.
A companion report from the Oregon Department of Fish and Wildlife estimates that removing the sea lions doing the most damage saved some 1,655 salmon.
Department spokesman Rick Hargrave said the hazing and removal of California sea lions will continue next year with few changes. One difference will be trying to block areas near the dam where the sea lions can get out of the water to rest.
California sea lions are normally protected by federal law. But since some have discovered that salmon - including threatened and endangered species - are easy pickings at the dam, NOAA Fisheries Service has given authority to the states of Oregon, Washington and Idaho to kill up to 85 a year. This was the first year sea lions were killed as well as trapped and sent to aquariums.
Meanwhile the 9th U.S. Court of Appeals heard arguments in Portland, Ore., Friday on the Human Society's lawsuit trying to stop the program. A trial judge rejected the organization's arguments that dams and fishermen kill more fish than the sea lions, and the appeals court has refused to halt the trapping while the case is in the court.
The Army Corps report also found that a few sea lions were hanging around the dam in the fall for the first time, raising concerns they could start feeding on fall and winter salmon runs. It also found the numbers of white sturgeon eaten, particularly by the Stellar sea lions, continued to increase, hitting an estimated 1,710 this year.
©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Explore further: Climate change may have little impact on tropical lizards