the film
Ecology and salmon related articles

Tests Find More Cases of Salmon Sex Change

by Dan Hansen
Spokesman Review, November 8, 2001

Zoologist says Hanford Reach results duplicated on Yakima, lower Columbia

A study that last year indicated male salmon from the Hanford Reach may be changing sex and spawning as females has been repeated on the Yakima and lower Columbia rivers with similar results.

University of Idaho zoologist Jim Nagler said researchers aren't sure what to make of the results. The most obvious conclusion is that the sex change is occurring for some environmental reason, since the same tests have turned up negative in salmon from Vancouver Island streams.

But it's also possible there's some genetic difference between chinook salmon from the Columbia River basin and those from Canada -- a difference that would make it appear the sex change is occurring even if it isn't.

Nagler cautioned that it's far too early to draw conclusions. It could take years to prove whether gender-bending is happening, and much longer to determine the cause of the mutation -- whether it's a chemical in the water, the temperature of the water, river-flow fluctuations or other environmental causes.

"We have some interesting observations but I think it will be a number of years before we hammer out what is going on here," Nagler said. "We have to come at the problem from a number of unrelated angles."

Armed with a $100,000 grant from the Bonneville Power Administration, Nagler and other researchers from UI and Washington State University plan another two years of studies.

Last year's study, which attracted national attention, showed that 80 percent of the female chinook collected at Hanford Reach of the Columbia had genetic "markers" that indicated the presence of both "X" and "Y" chromosomes.

Typically, females of any species carry only X chromosomes, while males have both X and Y. That way, any offspring are as likely to be females as males.

Researchers fear that females with a Y chromosome will produce an inordinate number of males, including some with Y chromosomes only. Those "super-males" would be unable to produce any female offspring.

When researchers last year tested hatchery fish that are genetically identical to those from the Hanford Reach, they found no indication that any had changed sex. But this year's results were different: even some of the hatchery females had Y chromosomes.

"I don't have an answer" for the disparity between this year's and last year's tests of hatchery fish, Nagler said. "Did we sample some fish last year that were late returning (from the ocean to the hatchery) and now these are early returning fish? Or was there some other abnormality?"

One thing's been ruled out: Scientific error within the test itself.

The American researchers sent unmarked samples of the male and female chinook they tested to the Canadian lab that developed the technique. That lab, which has never found sex-change evidence in Vancouver Island fish, "ran the tests on our fish and found exactly what we found," Nagler said.

Dan Hansen
Tests Find More Cases of Salmon Sex Change
Spokesman Review, November 8, 2001

See what you can learn

learn more on topics covered in the film
see the video
read the script
learn the songs
discussion forum
salmon animation