Fish Reproduction Symposium Probes Intricacies of Sex
MOSCOW, Idaho --The genetic intricacies of salmon sexes and the apparent effects of pollution on both Puget Sound and Lake Mead fishes were among topics reported on by scientists gathered here this week for a symposium on salmon recovery.
Sponsored by the University of Idaho -- Washington State University Center for Reproductive Biology and the National Marine Fisheries Service Northwest Fisheries Center in Seattle, the symposium drew nearly 70 scientists primarily from the Northwest.
Researchers from universities and tribal, federal and state fisheries departments spent two days reviewing the question of whether pollution in popular waters is affecting fish reproduction, salmon genetics and conservation efforts.
In Las Vegas Bay, an arm of Lake Mead that is fed by 130 million gallons of treated sewage and other contaminated industrial runoff, U.S. Geological Survey scientist Steven Goodbred reported on an extensive study of carp, razorback suckers and largemouth bass.
That work, among the longest running studies of its kind ever undertaken, did find evidence that the fishes showed reduced levels of sex hormones, primarily testosterone.
The result is that both the development of male fish and sperm quality is reduced in fish found in Las Vegas Bay, Goodbred said.
Lyndal Johnson, a National Marine Fisheries Service scientist at Seattle, reported on work in Puget Sound. She said the agency found a strong correlation between abnormal levels of a sex hormone derivative in English sole and the fishes' proximity to major sewage outfalls.
The study sampled areas ranging from heavily developed Elliott Bay near Seattle to near pristine Hood Canal.
University of British Columbia scientist Luis Afonso reported that tests with young chinook salmon exposed to estrogenic compounds, undiluted bleached kraft pulp mill effluent and diluted sewage effluent did show apparent sex reversal.
They reported their findings during a session led by James Nagler, a UI assistant professor of biology, who sampled fall chinook from the Columbia River's Hanford Reach. He found many of the females carried genetic markers that suggested they began life as males.
Whether that showed the fish had reversed sex early in development or were merely biological oddities remained open to speculation, Nagler said.
Nagler reported that subsequent sampling in the Hanford Reach, Yakima River and below Bonneville Dam showed the phenomenon occurred elsewhere in the basin as well but there was no apparent pattern.
WSU zoology professor Gary Thorgaard, who worked with Nagler on the original study published in late 2000, led another session about the state of the current science of salmon sex determination.
Thorgaard reported that his team at WSU is continuing to work on a definitive test. Scientists also reported during the session on their efforts to find genetic markers that indicate the genetic sex of salmon.
Other scientists from WSU, NMFS, U.S. Geological Survey and the University of British Columbia all reported their own efforts to find the still-elusive definitive genetic test for sex in salmon.
Another panel led by NMFS scientist Penny Swanson of Seattle focused on various strategies to preserve the genetic heritage of Northwest salmon runs.
Panelists included UI zoology professor and conference organizer Joseph Cloud, who reported on efforts to preserve salmon sperm by freezing it in liquid nitrogen. He also reported on work to preserve ovarian tissue from females.
Cloud reported that he and Nagler had successfully transplanted testes that had been cryogenically preserved and induced them to produce sperm. They have also transplanted frozen ovarian tissue but whether the females will produce eggs is still more than a month away.
Cloud said the conference reflects the close working relationship of UI and WSU scientists and the Center for Reproductive Biology. He said plans are in the works to establish a closer working relationship with scientists on the two campuses and the National Marine Fisheries Service Northwest Fisheries Center, which is based at Seattle.
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