Chinook salmon run was late, but sizable

PORTLAND – For a while, it looked like the Columbia River’s spring chinook salmon run might give 2006 a miss. Fishing seasons were curtailed and tribal fisheries were reduced as fish biologists waited – and waited – for the fish to arrive at Bonneville Dam.

But then the fish arrived – in bigger numbers than last year.

When the counting season closed on Wednesday nearly 124,000 chinook had passed the dam, more than the 88,000 expected and more than last year’s return of 95,000.

“This year’s spring run took its time but it crossed the finish line with a very respectable showing,” said Bob Lohn, head of the Northwest region of the National Oceanic and Atmospheric Administrations fisheries service. “The long-term average continues to rise.”

While the run usually peaks in mid-April, the salmon did not even begin arriving at Bonneville Dam in significant numbers until the first week of May.

By mid-April only 135 adult chinook had been counted at the dam. The 10-year average at that point, which includes a couple of bumper years, is about 19,000.

It was the second year in a row the run was seriously tardy. Nobody is sure why or what finally sent them on their way upriver.

Lohn credited improvements in fish passage facilities at the dams, hatchery and harvest management and better fish habitat for the eventual healthy return.

Fish biologists considered a number of factors as possible causes for the delay, including ocean conditions and, more recently, hordes of hungry sea lions who camp out in the river just below the dam seeking an easy snack when the fish gather to go up the fishways over the dam on their way up the Columbia.

Bonneville, about 45 miles upriver from Portland and some 150 river miles from the Pacific Ocean, is the first of many dams the fish must navigate as they return to where they were hatched to spawn.

Some of the sea lion exclusion devices that keep the mammals from getting into the fish ladders were removed temporarily to see if it improved fish passage, but biologists could detect no real difference.

The devices are meant to keep the sea lions out of the stairstep-like fish ladders the fish use to pass Bonneville and other dams.

By some accounts, the sea lions eat about 3.5 percent of the run as it heads upriver.

Lohn said poor ocean conditions in 2004 and 2005 may mean a smaller return in 2007. He said early upriver returns from fish that migrated to the ocean in 2004 and 2005 are about a third less than last year, which could mean fewer returning adults next year.

“Our scientists are about to complete important research on the huge influence that changing ocean conditions have on salmon from the time they migrate as juveniles through the estuary into the ocean to when they return as adults,” Lohn said.

It may help identify the biological trigger that sends the fish upriver, and what pulls it.

The U.S. Army Corps of Engineers is installing fish slides on some dams on the Snake River, a major Columbia tributary, to increase survival of young salmon headed to sea.

Meanwhile, an NOAA Fisheries scientist told the Northwest Power and Conservation Council in Boise this week that adult salmon and steelhead at and between hydroelectric dams on the two rivers is averaging 98 percent or better in recent years.

“That’s real high survival. Most people would agree those are good numbers to have,” said Ritchie Graves, acting branch chief of NOAA Fisheries regional Hydropower Division in Portland.

NOAA Fisheries is the federal agency that implements the Endangered Species Act for salmon and steelhead in the Northwest.