LEWISTON – U.S. Army Corps of Engineers biologists will kill more double-breasted cormorants this year to see if the predators are gorging themselves on juvenile chinook salmon, hampering recovery of the endangered species.
The agency, which has a permit to kill 60 of the fish-eating birds along the Lower Snake River, plans to examine the contents of their stomachs. Forty cormorants were killed and examined in December 2007 after concerns arose that they were moving upriver toward Lewiston and neighboring Clarkston.
That effort showed the birds taken near Lower Granite Dam in Washington were eating shad, not young salmon; this year, the cormorants will be killed later in the winter when water temperatures cool and shad have left the river system, to see if the birds alter their diet.
“Hopefully we will not find anything – that would be the good thing,” said Scott Dunmire, a fisheries biologist with the corps at Walla Walla. “If we do, we will evaluate that.”
A survey done by the Army corps in 2004 on a colony of 18,000 cormorants in the Columbia River estuary along the Washington and Oregon border found that the birds ate 6.5 million juvenile salmon and steelhead that year. The corps is in the process of trying to disrupt and move breeding colonies of cormorants and terns in the lower Columbia River.
Similar measures could be taken on stretches of the Snake River if cormorants become a hindrance to salmon recovery.
“I would hate to see those birds start thriving more and then really have an impact on salmon,” Dunmire said. “We want to protect the fish, and that is why we are doing the research.”
He’s not sure where the cormorants originate. But he’s fearful the birds moving upriver to feed on populations of shad could spend relatively mild winters around Lewiston, shifting to juvenile fall chinook once water temperatures cool and shad depart.
Most of the cormorants will be killed near Lower Granite Dam, but Dunmire said birds could be taken closer to Lewiston.