10-4-07

Salmonid Hatcheries Cause "Stunning" Loss of Reproductive Ability

By David Stauth, 541-737-0787



Contact: Michael Blouin, 541-737-2362



CORVALLIS, Ore. - The rearing of steelhead trout in hatcheries causes a

dramatic and unexpectedly fast drop in their ability to reproduce in the


wild, a new Oregon State University study shows, and raises serious

questions about the wisdom of historic hatchery practices.

The research, to be published Friday in the journal Science,
demonstrates

for the first time that the reproductive success of steelhead trout, an

important salmonid species, can drop by close to 40 percent per

captive-reared generation. The study reflects data from experiments in

Oregon's Hood River.

"For fish to so quickly lose their ability to reproduce is stunning,
it's

just remarkable," said Michael Blouin, an OSU associate professor of

zoology. "We were not surprised at the type of effect but at the speed.
We

thought it would be more gradual. If it weren't our own data I would
have

difficulty believing the results."




Fish reared in a hatchery for two generations had around half the

reproductive fitness of fish reared for a single generation. The effects


appear to be genetic, scientists said, and probably result from
evolutionary

pressures that quickly select for characteristics that are favored in
the

safe, placid world of the hatchery, but not in the comparatively hostile


natural environment.

"Among other things, this study proves with no doubt that wild fish and

hatchery fish are not the same, despite their appearances," said Michael


Blouin, an OSU associate professor of zoology. "Some have suggested that


hatchery and wild fish are equivalent, but these data really put the
final

nail in the coffin of that argument."




Even a few generations of domestication may have significant negative

effects, and repeated use of captive-reared parents to supplement wild

populations "should be carefully reconsidered," the scientists said in
their

report.

Traditionally, salmon and steelhead hatcheries obtained their brood
stock

and eggs from fish that were repeatedly bred in hatcheries - they tended
to

be more docile, adapted well to surface feeding, and they thrived and

survived at an 85-95 percent level in the safe hatchery environment.

More recently, some "supplementation" hatchery operations have moved to
the

use of wild fish for their brood stock, on the theory that their
offspring

would retain more ability to survive and reproduce in the wild, and
perhaps

help rebuild threatened populations.

"What happens to wild populations when they interbreed with hatchery
fish

still remains an open question," Blouin said. "But there is good reason
to

be worried."




Earlier work by researchers from OSU and the Oregon Department of Fish
and

Wildlife had suggested that first-generation hatchery fish from wild
brood

stock probably were not a concern, and indeed could provide a short-term


boost to a wild population. But the newest findings call even that

conclusion into question, he said.

"The problem is in the second and subsequent generations," Blouin said.

"There is now no question that using fish of hatchery ancestry to
produce

more hatchery fish quickly results in stocks that perform poorly in
nature."




Evolution can rapidly select for fish of certain types, experts say,
because

of the huge numbers of eggs and smolts produced and the relatively few
fish

that survive to adulthood. About 10,000 eggs can eventually turn into
fewer

than 100 adults, Blouin said, and these are genetically selected for

whatever characteristics favored their survival. Offspring that inherit

traits favored in hatchery fish can be at a serious disadvantage in the
wild

where they face risks such as an uncertain food supply and many
predators

eager to eat them.

Because of the intense pressures of natural selection, Blouin said,
salmon

and steelhead populations would probably quickly revert to their natural


state once hatchery fish were removed.

However, just removing hatchery fish may not ensure the survival of wild


populations. Studies such as this consider only the genetic background
of

fish and the effects of hatchery selection on those genetics, and not
other

issues that may also affect salmon or steelhead fisheries, such as

pollution, stream degradation or climate change.

Blouin cautioned that these data should not be used as an indictment of
all

hatchery programs.

"Hatcheries can have a place in fisheries management," he said. "The key


issue is how to minimize their impacts on wild populations."




This research was conducted through use of 15 years of DNA tracking

technology of fish breeding in Hood River, a mountain stream that flows

northward off Mount Hood into the Columbia River. DNA analysis with
scales

was done with about 15,000 fish since 1991.

This research has been supported by the Bonneville Power Administration
and

the Oregon Department of Fish and Wildlife.