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Spring Run Fizzles:
Mysteries of the Deep Deepen

by Bill Rudolph
NW Fishletter, June 2, 2004

The spring chinook run on the upper Columbia River is turning out to be something of a disappointment, with only 170,000 fish counted at Bonneville Dam by the end of May, but it's still 30 percent above the 10-year average.

Harvest managers predicted a 360,000-fish return for 2004, based largely on the signal from last year's jack returns. That would have made it the second largest spring run since 1938. But managers have now downgraded the spring run to about 190,000 fish (estimated to river mouth) and are at a loss to explain what happened.

"Maybe it's time to find a new profession like weather forecasting," joked Washington Department of Fish and Wildlife's Cindy LeFleur, who heads the technical committee that crunches the numbers. LeFleur said the group had no explanation for the declining numbers, so far. Age composition of the returning fish seemed normal, she said, with most upriver fish having spent the last two years in the ocean.

The latest revision is close to the pre-season expectation for the Snake River run alone. So far, about 60,000 chinook have actually been counted at Lower Granite Dam, about half of what was expected, says NOAA Fisheries' Jerry Harmon, who leads the crew that mans the adult fish trap at Granite, the last dam where fish pass before they enter Idaho.

"I don't have an answer," Harmon said, who noted that the more than 8,000 jacks (precocious males) counted last year would usually mean a much larger run would appear at the dam. He suggested that maybe the jack-to-adult ratio used by harvest prognosticators needs to be reworked. In earlier years, when hatcheries held juvenile chinook longer before release, more fish returned as jacks. "Bigger smolts--more jacks," he said. "Maybe that's happening again."

Harmon also noted about 20 percent to 30 percent of the returning chinook have evidence of marine mammal bites, as in years past. He said measurement of the teeth marks shows they were probably inflicted by harbor seals, not sea lions. "We never see sea lion bites," Harmon said. "I think they always get their prey."

Sea lions have taken some blame this year for reduced fish numbers, but Corps of Engineers biologist Robert Stansell thinks their effect is not as great as fishermen have said. Stansell estimated that the 100 or so sea lions around Bonneville Dam have eaten about 2 percent of the run passing by this spring. He couldn't estimate the salmon take from other sea lions in the estuary, with about 1,200 estimated to be hanging out near the mouth of the Columbia at Astoria before they head south to breed in California waters.

Others think sea lions, whose populations have been growing at 8 percent annually, are having a much greater effect. Oliver Waldman, executive of Salmon For All, a commercial fishermen's' advocacy group based in Astoria, points to gillnetter tales this spring of having whole nets stripped of salmon by sea lions. Waldman said a conservative estimate could peg the sea lion harvest of spring salmon at 50,000 fish.

However, some spring runs are coming in at numbers close to pre-season estimates, said WDFW's Joe Hymer. He pointed to returns in the Willamette, Cowlitz and the Lewis rivers as "performing as planned."

It's the upriver runs that seem to be behind, Hymer said, who noted those stocks migrate farther north and farther out into the North Pacific than the lower Columbia runs which generally stay close to the coast between the river and Vancouver Island.

This year's smelt run came in below expectations as well, Hymer said, which suggests something happened in the ocean to reduce overall productivity. There's some evidence that smelt populations that usually forage in offshore shrimp beds suffered compared to those that stay in the kelp beds around Vancouver Island, Hymer said. With fall chinook migrations generally inshore compared to springers, Hymer is still looking forward to a great fall chinook season.

Bill Rudolph
Spring Run Fizzles: Mysteries of the Deep Deepen
NW Fishletter, June 2, 2004

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