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Ref:644/03 |
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canada
- Mar 29, 2003 |
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Hatchery fish debate
grows
Scientists in Canada find evidence
that captive breeding can cause genetic problems |
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JEFF BARNARD - The
Associated Press
GRANTS PASS — Scientists
have found that salmon raised at a Canadian fish
farm produced smaller and more numerous eggs.
The finding adds to concerns that using hatchery
fish to rebuild endangered populations may produce
offspring less able to survive in the wild.
The
big eggs characteristic of fish spawning in the
wild become smaller when wild fish interbreed with
hatchery fish carrying the genetic trait for
smaller eggs, researchers found. |
The Associated Press file
A scientist at the Yellow Island Aquaculture
Limited hatchery in British Columbia, Canada,
holds hatchery salmon eggs that researchers say
have declined in size by 25 percent. |
Smaller eggs generally produce smaller fry, or
juvenile salmon, which are considered less able to
compete for food.
“It’s sort of a cautionary tale for salmon
enhancement efforts,” said Daniel Heath, the
holder of the Canada research chair in
conservation genetics at the
University of Windsor in
Ontario and lead author of the study
published in the journal Science.
“On the bigger question of captive breeding in
general, it could potentially drive evolution
because it’s in a benign environment,” he said.
Researchers examined the size of eggs produced by
chinook salmon during the past 12 years — four
generations — at Yellow Island Aquaculture Ltd. in
British Columbia.
They found the size of eggs declined by 25 percent
in that short time. The smaller size of eggs meant
salmon could produce more eggs.
“When we were looking at the data, I was amazed —
and the co-authors as well — at the size of this
effect,” Heath said. “Without even knowing it,
they were selecting for traits that would make
them do well in a captive environment. As far as I
know, this is the first time this has ever been
demonstrated.”
The genetic trait for small eggs “just swept
through the population,” said Heath.
The study adds to the debate regarding the
differences between wild salmon and hatchery
salmon, and how best to rebuild the 26 populations
of Pacific salmon and steelhead that are
classified as threatened or endangered species on
the West Coast.
Property rights advocates are suing the federal
government in an effort to overturn Endangered
Species Act protections for some salmon runs,
arguing that hatchery fish should be counted along
with wild fish in determining whether a population
is in danger of extinction.
As the result of one of those cases,
NOAA Fisheries,
formerly known as the National Marine Fisheries
Service, is re-examining Endangered Species Act
status for Pacific salmon and developing a new
policy on how hatcheries fit into efforts to
rebuild declining runs.
Robin Waples, a senior scientist for NOAA
Fisheries, said salmon populations generally seek
a genetic balance between large eggs, which
produce young fish that compete better for food,
and small eggs, which are more numerous. The
environment determines what mix of those traits
produces better survival for the population as a
whole.
“This is one of the unanswered questions about
supplementation,” of wild populations with
hatchery fish, said Waples. “The whole point of a
hatchery is you have a lot of fish survive. You
have the potential for a short-term demographic
boost. What is not known is what are the long-term
consequences of this.
“The inevitable tradeoff is genetic change, and
that tradeoff is not likely to be beneficial,”
Waples added. “It’s one of the reasons we’ve
argued supplemental programs should be considered
experimental.”
The study adds to an already strong body of
evidence suggesting that hatchery fish hurt,
rather than help, rebuild declining runs, said
Bill Bakke of the Native Fish Society, a
conservation group.
“Some researchers suggest that the only thing wild
fish and hatchery fish have in common is water,”
said Bakke. “The problem is having hatchery fish
breeding with wild fish. What usually comes out of
that is some intermediate level of survival.” |
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