[env-trinity] Times Standard May 18, 2009
bwl3 at comcast.net
Mon May 18 10:10:33 PDT 2009
Fish food: Trinity River study looks into how hatchery fish eat wild fish
John Driscoll/The Times-Standard
Posted: 05/18/2009 01:30:13 AM PDT
The debate over how hatchery-produced salmon and steelhead can be used to
bolster runs of wild fish has long been the source of controversy -- and a
new study on the Trinity River has reawakened that discussion.
There is a long list of troubles biologists assign to mixing hatchery fish
with wild fish. They can compete for food, pass on disease and genetically
mingle with naturally-produced fish. A recently completed Humboldt State
University master's thesis also looks at how many young wild fish are eaten
by the relatively large, voracious steelhead released from Trinity River
Hatchery each year.
It's prompted many involved with the restoration of the Trinity River and
its fishery to question how the hatchery is operated, and whether that
operation may be running counter to some of the goals of its restoration
program. The Trinity River Restoration Program, authorized in a 2001 U.S.
Interior Secretary's decision, sets goals to get 40,000 naturally spawned
steelhead to return to the river, and 10,000 hatchery fish to return to the
Since 2002, the numbers of both wild and hatchery fish have been generally
rising. But hatchery fish have far outpaced wild fish in terms of
production. For example, in 2006, about 8,000 wild fish returned to the
river, while about 32,000 hatchery fish returned. In 2007, about 47,000
hatchery fish returned compared to 7,000 wild fish.
The hatchery was built to make up for the loss of 109 miles of prime
spawning habitat above Trinity Dam. The restoration program, among many
other things, looks to improve habitat below the dam and release more water
than was released in the decades after the dam was built.
HSU fisheries graduate Seth Naman found in his short-term study that tens of
thousands of fry produced by fish spawning in the river are eaten by
hatchery steelhead released by the hundreds of thousands just below the dam
in March, as eggs are hatching in the river.
About 9 percent of the fry of natural chinook and coho salmon and steelhead
are consumed in the 2-mile reach of river Naman studied -- a stretch where
particularly high concentrations of fish spawn. Naman points out that he
didn't account for hatchery-produced coho salmon, which also likely eat
salmon and steelhead fry.
About 61,000 wild fry were eaten by some 437,000 hatchery steelhead from
late March to late April, according to Naman's estimate, with more likely
consumed in the following weeks.
"What I was trying to show is the potential for conflict between hatchery
fish and attempting to restore the river for naturally-produced fish," Naman
said in an interview.
Naman now works for the National Marine Fisheries Service, one of the
agencies involved in recommending policy for the hatchery, which is funded
by the U.S. Bureau of Reclamation but operated by the California Department
of Fish and Game.
Fish and Game associate fishery biologist Wade Sinnen raised some concerns
about the study, but also said it has merit. In many ways, the study backs
up what biologists have long known:
"When you put a predator like a steelhead out in the river, they will eat
fry," Sinnen said.
Sinnen said the hatchery tries to release steelhead when they are large
enough to begin making their way to the ocean, so they aren't hanging around
eating wild fish fry and competing for food and space. He said there's been
lots of discussion about how the Reclamation Bureau's goals for the hatchery
might be changed to make it more dynamic.
That complex question runs up against the fact that the spawning habitat
above the dam is cut off, and it's unlikely that the remaining river habitat
can produce, on its own, enough fish to meet the goals of the restoration
National Marine Fisheries Service Area Office Supervisor Irma Lagomarcino
said that she's concerned that the operation of the hatchery may be working
against the restoration program's goals.
"Are we building a system just for hatchery fish to occupy?" Lagomarcino
A plan to examine the effects of the hatchery has been the topic of talks
between state and federal agencies, the Hoopa Valley and Yurok tribes, and
fishing and environmental groups, Lagomarcino said.
How the hatchery's operations could be changed is an open question. The
timing of hatchery fish releases, the number of fish released, the size at
which they are released, the species of fish released and other factors are
all possible considerations.
A recent report commissioned by Congress on the Columbia River basin
recommended that hatcheries not harm habitat, that hatchery fish should be
either genetically separated or integrated with wild fish, and that their
success should be judged by adult returns, not how many fry are released.
Conservation groups and the Trinity Management Council -- agencies and
tribes that advise the restoration program -- and a stakeholder's working
group last spring asked Fish and Game leadership and the Reclamation Bureau
to develop a list of changes that might be considered at the Trinity River
Reclamation Bureau Mid-Pacific Region Area Manager Brian Person said that a
response is long overdue, but that the issue has proven particularly
complicated. As of now, Person said, there does not appear to be any
conflict with the agency's contract with Fish and Game in changing hatchery
operations. However, the complicated scientific issues -- and trying to find
some consensus on them -- are particularly delicate, he said.
"It's just not that simple," Person said, adding that a response is being
Tom Weseloh with California Trout said Naman's study outlines one of a slew
of problems associated with hatcheries. But while the goals of the Trinity
River Restoration Program are to allow for predominately wild fish, there is
a reality to deal with: The existence of the dam, the amount and timing of
water diversions to the Sacramento River and flows to the Trinity River all
make for a significantly different system than existed before the dam was
built, he said.
Ideally, hatchery fish should have as little effect on wild fish as
possible, he said, while still yielding fishery benefits. While both
hatchery and wild fish both began to increase in numbers for several years
after flows were increased early this decade, last year was a particularly
poor year, introducing more complexity to the issue. Weseloh said it may be
prudent to make some minor adjustments to hatchery operations instead of
wholesale changes, and adjust as the effects are realized.
"That's not that radical an idea," Weseloh said.
Naman's study is one of few done on hatchery fish eating wild fish fry, and
HSU fisheries department chairman Dave Hankin said it's difficult to
determine the impacts on the Trinity River's entire wild salmon and
steelhead populations. Naman's study is likely to raise awareness and
concern about predation, and how to avoid the effects of it, Hankin said.
"The issue of competition between wild fish and releases of hatchery fish
requires lots more attention than has been given it," Hankin said.
Byron Leydecker, JcT
Chair, Friends of Trinity River
PO Box 2327
Mill Valley, CA 94942-2327
415 383 4810 land
415 519 4810 cell
<mailto:bwl3 at comcast.net> bwl3 at comcast.net
<mailto:bleydecker at stanfordalumni.org> bleydecker at stanfordalumni.org
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