the film

Mystery of the Missing Chinook

by Allen Thomas, Staff Writer
The Columbian, January 5, 2006

A combination of factors appear responsible for Columbia River spring chinook runs falling far short of the forecast in the past two years, the most important being worsening ocean survival conditions. State, federal and tribal biologists completed a review in November why the Columbia's spring chinook returns were so far below predictions in 2004 and 2005.

Each December, the states make a forecast of how many spring chinook are expected to enter the river from February through mid-June destined for waters upstream of Bonneville Dam.

The forecast is an important number. Harvest rates allowed under the federal Endangered Species Act for sport and commercial fishermen in the lower Columbia are based on the forecast.

But in 2004 and 2005, the model used to forecast the spring chinook run went badly awry. In 2004, the forecast was for a run of 360,700, while the actual return was 193,400, just 54 percent of the prediction.

In 2005, the forecasting model missed even worse. The prediction was 254,100, compared to an actual return of 105,000, only 41 percent of what was expected.

Curt Melcher of the Oregon Department of Fish and Wildlife said, historically, the model has performed well, usually coming within 20 percent of the actual spring chinook return.

"In 2004 and 2005, for whatever reason, the predictor model performed very poorly,'' Melcher said. "We're all struggling with that.''

The biologists looked at a variety of factors and determined the following:

Columbia Spring Chinook Forecasts
Year Forecast Actual Percent
2000 134,000 178,700 133%
2001 364,600 416,500 114%
2002 333,700 295,100 82%
2004 360,700 193,400 54%
2005 254,100 105,000 41%

Allen Thomas
Mystery of the Missing Chinook
The Columbian, January 5, 2006

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