Puzzling piscine sex reversals have left salmon researchers scratching their heads. A study released by the University of Idaho and Washington State University reported that of the female salmon sampled, 84 percent tested positive for a male genetic marker, suggesting that these females actually began life as males.

Sex reversals could hold clues to declining salmon numbers, says James Negler, University of Idaho zoologist and co-author of the study. Negler says environmental contaminants may simulate hormones and induce sex reversals, or that changes in water temperature could be a cause, but more research is needed before definitive conclusions can be drawn. If this condition persists, the offspring of sex-reversed salmon could hold an aberrant YY genotype and breed only males, leading to a skewed male-to-female ratio in the salmon population.

Pat Ford of Save Our Wild Salmon finds it "worrisome" that this discovery materialized in what is considered to be the healthiest population of wild salmon in the Northwest. "From the point of view of salmon advocates, it's not a good thing," says Ford. "It seems to be another confirmation that we've got a sick river."

Read more about this study online at uidaho.edu/salmon.