Study Examine Salmon Eggs From Farms
Thu Mar 13, 5:57 PM ET
Science - AP
By JEFF BARNARD, Associated Press Writer
GRANTS PASS, Ore. - Salmon raised at a Canadian fish farm
rapidly evolved to produce smaller eggs, according to a study
that heightens doubts about whether hatchery-bred fish can
be successfully released into the wild to rebuild endangered
Smaller eggs generally produce smaller young fish. And smaller
fish do not compete for food in the wild as effectively as
"It's sort of a cautionary tale for salmon enhancement efforts,"
said Daniel Heath, an expert on conservation genetics at the
University of Windsor in Canada and author of the study in
Friday's issue of the journal Science.
Researchers examined eggs produced by four generations
of chinook salmon over the past 12 years at Yellow Island
Aquaculture in British Columbia, Canada. They found that the
fish produced more eggs, but the size of the eggs declined by
25 percent as wild fish interbred with hatchery fish.
Hatchery fish develop a genetic tendency to produce smaller
eggs because in hatcheries, there is no competition for food
the way there is in the wild. The lack of competition means
smaller fish can more easily survive.
As a result, the genetic trait for small eggs "just swept
through the population," Heath said.
The study complicates the debate over how best to rebuild
the 26 populations of Pacific salmon and steelhead that are
classified as threatened or endangered species.
Conservationists said the Canadian study shows that hatchery
fish do not help to rebuild declining runs.
"Some researchers suggest that the only thing wild fish and
hatchery fish have in common is water," said Bill Bakke of
the Native Fish Society. "What usually comes out of that is
some intermediate level of survival."
About 5 billion young fish are released from hatcheries each
year around the Pacific Rim.
Hatchery fish are not generally used to supplement wild
populations, but to provide fish for sport and commercial
fisheries. The two groups do occasionally breed, however.
On the Net:
NOAA Fisheries: http://www.nwr.noaa.gov
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