Diving ducks dine on endangered fish

WENATCHEE — Dam operators researching birds that prey on endangered fish in the mid-Columbia River should have been looking to demure ducks swimming in the water instead of blaming high-flying gulls, according to preliminary findings of a study.

The merganser consumes more young salmon and steelhead than any other bird along the reservoirs of Rock Island and Rocky Reach dams, University of Washington researcher Julia Parrish said. The swimming duck accounts for nearly two-thirds of the salmon taken by birds.

“They are the unknown predator that you’ve had in your system the whole time,” Parrish told commissioners with the Chelan County Public Utility District. “Yet there is no management of the merganser in the Columbia.”

The utility hired Parrish in 2002 to study bird predation on salmon. The $3 million study is the first comprehensive look at salmon-eating birds on the Columbia, and the results likely will be used by dam operators throughout the river system to manage the predators.

The work was expected to focus primarily on California gulls, ring-billed gulls, Caspian terns and double-crested cormorants.

Parrish said that when she started the study, she expected to verify a commonly held belief that gulls were the greediest salmon-eaters among all the birds. Instead, she found the merganser was swimming right under the radar of dam operators.

Also surprising was that the feed was occurring in the calm reservoirs behind the dams.

Eighty percent of all the fish eaten by birds are caught in the reservoirs behind the dams, not below them, the study found.

The utility’s wildlife experts were surprised by the findings.

“For years, we’ve thought that all the mortality occurred right below the dams, and that it was gulls and terns doing all the eating,” Todd West, the utility’s fish and wildlife supervisor, said.