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NW Fishletter #274, May 6, 2010

[3] Spring Chinook Run--More Than Half Over?

With every passing day, it is looking less likely that the upriver spring chinook run will hit harvest managers' original expectation--close to half a million fish by June 15. On the other hand, they said the adult count of more than 158,000 through May 3rd is the largest since 2002 and the third highest since 1977.

Based on passage to date, the harvest managers provided an admittedly unreliable 310,000-370,000 fish return prediction in a joint staff report yesterday. They said the run seems to be earlier than the past five years and they expect it to hit the 50-percent mark sometime this week.

Another passage predictor developed by the University of Washington has estimated that about 63 percent of the upriver run had passed Bonneville Dam by May 2, and pegged the return at about 262,000 fish. A different UW analysis pegged the return to Bonneville at 49 percent.

Springers have begun showing up at Lower Granite Dam near the Idaho-Washington border, more than 2,000 a day, with a total that reached above 20,000 by May 4.

So far, it's tracking close to the 10-year average, and IDFG expects an 180,000-fish return, which includes about 29,000 wild springers. But last year, only 320 spring chinook had been counted at Lower Granite by this date. Eventually, 50,000 hatchery and wild fish were counted, with about 50 percent of last year's run passing the dam by May 25. Fish counters may have a long way to go.

Harvest managers recommended opening select areas in the lower Columbia for two more days of commercial gillnetting to target locally produced chinook. They said test fishing had shown these local stocks are now abundant. "Fish are arriving at local hatcheries and it is important to harvest these fish before more escape into tributaries," said the report about the Youngs Bay area near Astoria.

Even though fishermen had netted more upriver fish in these out-of-mainstem areas than expected, managers said the upriver allotment to commercials remained within ESA limits. Out of nearly 9,000 springers caught in the select areas, about 1,300 were upriver-bound (including release mortalities). Altogether, gillnetters had caught 18,000 or so, with nearly half upriver chinook.

Sport fishers had caught more than 26,000 spring chinook in the Columbia this season, and their season is now closed below Bonneville Dam, though it is open in the Willamette River and above Bonneville.

Spring chinook numbers in the Willamette have improved immensely since last year. More than 15,000 have been counted at the Falls already, more than last year's entire return. ODFW is expecting almost 63,000 at the Falls, four times the return of 2008, and more than twice the size of last year's escapement.

With this year's good show of spring fish, more sea lions than ever have been showing up to chew on the chinook. Seventy-one of them were counted at Bonneville on April 15. Observers have recognized at least 55 different California sea lions and 53 Steller sea lions and one harbor seal, according to the latest hazing report from the Corps of Engineers.

More than two dozen of the California sea lions have been seen here before, and 21 seen this year are on the list for removal. Nine have already been removed.

Even with so many marine mammals in the vicinity of the dam, the report says the 3,400 salmon taken by them is the lowest percentage of the run since 2004. But one particular sea lion, identified as C287 has been observed at sites upstream of Bonneville Dam, and known to consume at least 186 salmon this year. Last year, observers saw him catch 157 salmon, "the highest ever attributed to one animal in one season."

In other news, NOAA Fisheries has started a pilot program to investigate adult survival from the lower Columbia to Bonneville Dam. By PIT-tagging and acoustic tagging nearly 300 spring chinook caught in tanglenets this spring, researchers have begun a pilot study to study that stretch of the river where no estimates of adult salmon survival have yet been developed.

With more than 7,000 pinnipeds in the lower Columbia, including 3,000 California and Steller sea lions, and 4,000 harbor seals, who all take a bite out of the spring chinook run, the researchers say they will work closely with state and tribal biologists who actively track predators "to compile circumstantial evidence of predation based on observed species co-occurrence as an initial step, and then follow up with more complex studies to look at specific predator/prey interactions when they are warranted."

Some federal biologists have said before that marine mammals in the lower river could be preying on up to 20 percent of the spring run. -B. R.

The following links were mentioned in this story:

passage predictor

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