Steelhead numbers based on formulas

Thanks for the stories about the rebounding of the halfpounder steelhead run in the Rogue River this year. But one thing puzzles me. In each story, the halfpounder estimates seem to be going down even though the (Oregon Department of Fish and Wildlife) has counted more fish. What gives?

— Michael P., by e-mail

Well, Michael, welcome to the world of fish biology, where the only absolute about halfpounder run estimates is that it's better not to guess the numbers until all the counting's over.

"This is an example of why it can be confusing when start throwing out those numbers at mid-season," says ODFW fish biologist Todd Confer in Gold Beach.

The halfpounder estimates are based on counts of fish netted Mondays, Wednesdays and Fridays at Huntley Park on the Rogue east of Gold Beach. Those numbers are put into computer formulas that take into account river flows.

The flow helps estimate the "efficiency rate" of the netting, Confer says. When flows go up, the efficiency rate goes down and vice-versa, Confer says.

The changes came because the U.S. Geological Survey revised some of the flow estimates to lower levels on some of the days that ODFW crews caught high numbers of halfpounders, Confer says. Lower flows meant higher efficiency in catch rates those days, triggering lower estimates.

With the adjustments made, the latest estimate of about 118,800 halfpounders in the Rogue, Confer says. Though a hair lower than earlier estimates, it's still the best in several years.

Send questions to "Since You Asked," Mail Tribune Newsroom, P.O. Box 1108, Medford, OR 97501; by fax to 541-776-4376; or by e-mail to We're sorry, but the volume of questions received prevents us from answering all of them.

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