EPHRATA - A project to move Caspian terns off an island at the Potholes is paying dividends in steelhead survival around Wanapum and Priest Rapids dams.

At least that's the result of the first year, said Curt Dodson, fish biologist for the Grant County PUD. Dodson talked about fish passage and fish survival at the PUD commission meeting Tuesday.

The PUD is required to meet fish survival targets as part of its operation, Dodson said. Fish survival is calculated on a three-year timeline, he said, and over that three years 86.5 percent of juvenile fish must make it through the Wanapum-Priest Rapids complex for the PUD to meet its target.

The PUD has met its targets with juvenile chinook and sockeye salmon, Dodson said. The problem in the 2008-10 time frame (the latest information available) has been juvenile steelhead, he said.

Grant PUD is responsible for the portion of the Columbia River between the bottom of Rock Island Dam and the bottom of Priest Rapids Dam, he said. The PUD has been hitting steelhead survival targets as the fish pass the dams, he said, with most of the loss apparently occurring in the Wanapum and Priest Rapids reservoirs.

Dodson said the missing fish could've been eaten by birds or bigger fish, or could be choosing to stay put instead of migrating. Utility district officials used tags to track the steelhead, and found a lot of them on Goose Island in the Potholes, he said.

Goose Island was home to the largest colony of Caspian terns in eastern Washington, Dodson said. "They love steelhead." The U.S. Army Corps of Engineers and U.S. Bureau of Reclamation tracked 54 birds in 2013, he said, and discovered they flew far and wide to catch fish, but one of their favorite spots was the Wanapum and Priest Rapids reservoirs.

In 2014, the agencies tried to close Goose Island to the birds, Dodson said, which cut the population from 1,000 to 300. The reservoirs had been losing about 20 percent of the juvenile steelhead to bird predation between 2008 and 2010, Dodson said, and in 2014 that dropped to about 3 percent.

That meant the PUD met the target for 2014, but they have to maintain the average for at least two additional years, Dodson said.