Something's fishy with Columbia chinook: females carry male's genetic...( MOSCOW--Samples in 1999 from fall chi...)

MOSCOW--Samples in 1999 from fall chinook salmon in the Columbia River's Hanford Reach show that four-fifths of the females spawning there apparently began life as males.

The finding could provide an important clue in sorting through the complex reasons for the decline of Northwest salmon runs, although the Hanford's wild fall chinook run is among the healthiest. The researchers ruled out radiation as a possible cause of the apparent sex reversal but suggested environmental contaminants that mimic hormones or water temperature changes could be the culprits.

The research by University of Idaho and Washington State University scientists in cooperation with the Pacific Northwest National Laboratory was published in Environmental Health Perspectives, a journal of the National Institute of Environmental Health Sciences.

James J. Nagler, UI assistant professor of zoology who led the study, said the results of the genetic testing on the natural-spawning chinook came as a surprise.

"We have found that a majority of the female chinook salmon sampled carry a genetic marker that is found only in male salmon. The best explanation for these results is that these females have been 'sex reversed' and are in fact male," Nagler said. "This is not unheard of as salmon can be sex reversed experimentally under laboratory conditions. What is surprising is that this is the first report of this from a wild population of fish."

Gary Thorgaard, WSU's School of Biological Sciences director and a co-author of the paper, says that experiments in his laboratory and others have shown it is possible to reverse the sex of trout embryos through the use of hormones. A study in Canada showed changing temperature could alter the sex of young sockeye salmon.

Other authors include Jerry Bouma, UI graduate student, and Dennis Dauble, a salmon biologist at the Pacific Northwest National Laboratory operated by Battelle in Richland. Dauble, PNNL natural resources manager, has
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Contact: Bill Loftus
bloftus@uidaho.edu
208-885-7694
University of Idaho
14-Dec-2000