NFC: Re: Fwd: Salmon in Gender Crisis

[jake levi <jlevi_us at yahoo_com>]

FYI


> >>
> >>Salmon in Gender Crisis
> >>
> >>Source: AFP via Common Dreams
> >>Published: December 22, 2000
> >>
> >>SEATTLE - Sexual identity may be a problem facing
> the Pacific Northwest's
> >>endangered wild salmon runs, according to the
> findings of new research 
> >>into
> >>gender of the fish.
> >>
> >>A study of the chinook-salmon run in the Columbia
> River's most fertile 
> >>spawning
> >>ground late last year found that 80 percent of the
> spawning female fish 
> >>probably
> >>began life as males.
> >>
> >>The findings surprised the study's lead author,
> James Nagler, a University 
> >>of
> >>Idaho zoologist.
> >>
> >>"The research raises more questions than answers,"
> Nagler told AFP.
> >>
> >>He believes that the sex changes could be caused
> by pollutants or water
> >>temperature changes.
> >>
> >>However, ruled out as a cause is radiation seeping
> from the nearby Hanford
> >>Nuclear Reservation. The amount of radioactivity
> known to be going into 
> >>the
> >>river is too small to have produced such changes,
> according to the study's
> >>authors.
> >>
> >>The possible "sex reversal" of salmon could have a
> significant impact on 
> >>efforts
> >>to preserve the genetic traits of wild runs.
> >>
> >>The study by Nagler, Gary Thorgaard, a fish
> geneticist at Washington State
> >>University, and two other researchers, was 
> published last week in 
> >>Environmental
> >>Health Perspective, a journal of the National
> Institute of Environmental
> >>Sciences.
> >>
> >>Researchers sampled 50 female and 50 male chinook
> in Hanford Reach, the 
> >>last
> >>free-flowing stretch of the Columbia River  -- and
> its most fertile 
> >>spawning
> >>ground. Most of the female fish carried a genetic
> marker found only in 
> >>male
> >>salmon.
> >>
> >>"What we've got is an interesting observation with
> many unknowns," said 
> >>Nagler.
> >>
> >>"This could be a contributing factor, coupled with
> all the other burdens 
> >>on the
> >>backs of these fish, that tweaks the health of
> these populations. It could 
> >>be
> >>the tip of a pretty significant iceberg," he said.
> >>
> >>"There's no reason this couldn't happen," said
> Paul Bentzen, a geneticist 
> >>at the
> >>University of Washington Fisheries Department.
> "Sex determination is more
> >>relaxed in fish than in humans or other animals."
> >>
> >>Nagler said the sex of salmon has been changed
> under laboratory 
> >>conditions,
> >>usually through the concentrated use of hormones.
> For example, aquaculture 
> >>farms
> >>sometimes transform male salmon into females
> because the females often 
> >>grow
> >>larger and produce more desirable meat.
> >>
> >>But the phenomenon has never been seen in wild
> salmon stocks, according to
> >>Nagler and other researchers.
> >>
> >>Nagler's major concern about sex reversal in wild
> runs is that it might 
> >>create a
> >>"supermale" fish whose characteristics in the wild
> are unknown.
> >>
> >>Indeed, this may already have happened, the
> researchers conceded.
> >>
> >>Normally, female fish carry two X chromosomes,
> while males carry an X and 
> >>a Y
> >>chromosome. The altered females, which  produced
> eggs, spawned and died in 
> >>the
> >>normal cycle, also had an X and Y chromosome. Half
> their offspring could 
> >>wind up
> >>with two Y chromosomes, Nagler said.
> >>
> >>"It would be frightening if we're whittling down
> the female population and
> >>female genetic traits," said Nagler. "It might
> just be  a correcting thing 
> >>but
> >>my gut tells me that if you reduce female genetics
> in a species it's got 
> >>to have
> >>an impact."
> >>
> >>However, Nagler said that the effects on the
> offspring can be studied no 
> >>further
> >>until the salmon return to the Hanford Reach  to
> spawn. Future expanded 
> >>studies
> >>are being planned to determine if the sex
> reversals were a one-time event 
> >>or if
> >>other wild salmon runs have undergone similar
> changes.
> >>
> >>Thorgaard believes the most likely cause of the
> reversal is pollution from
> >>agricultural or industrial chemicals, which may
> act  like estrogens.
> >>
> >>By contrast, a study of fish from the same genetic
> stock from the nearby 
> >>Priest
> >>Rapids Fish Hatcher showed no evidence of
> sex-reversal.
> >>
> >>"It's unlikely this is naturally occurring," said
> Thorgaard.


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