[env-trinity] Hatchery v. Wild Fish Trinity Journal 4 29 09

Byron Leydecker bwl3 at comcast.net
Thu Apr 30 16:43:43 PDT 2009


There are numerous scientific studies that conclude similarly.I have several
of these,  If anyone would like these, let me know.

Byron

Swimming for their lives 
Wild fish face added threat from hatchery steelhead, study says 
By AMY GITTELSOHN 

Researchers have warned that hatchery-produced fish can harm wild stocks by
competing for food and habitat.



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http://www.trinityjournal.com/news/2009/0429/front_page/001p1_lg.jpg


Allen Houston, fish culturist at the Trinity River Hatchery, right, examines
newly hatched steelhead in the incubator and steelhead fingerlings to be
reared at the hatchery and released to the Trinity River in March of next
year. A recent study sought to determine the impact of hatchery fish on the
native fish population; the results are currently being debated. 

In a study on the Trinity River, a fisheries biologist reported a more
direct impact that Trinity River Hatchery steelhead have on wild fish. They
eat them.

Seth Naman conducted his research in 2007 in a study funded by the Yurok
Tribal Fisheries Program. Naman and his crew caught fin-clipped hatchery
steelhead on a two-mile section of the Trinity River downstream of the
Lewiston Dam, anesthetizing them, pumping their bellies and recording the
results before reviving them and sending them on their way.

Prior to the 2007 release of hatchery steelhead in March, they caught 315
"residualized" steelhead released from the hatchery in 2006 which stayed in
the river rather than migrating to the ocean. Those hangers-on had 435
salmonid fry and 2,685 salmonid eggs in their stomachs.



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http://www.trinityjournal.com/news/2009/0429/front_page/001p2_lg.jpg


 

In March 2007, the hatchery released yearling steelhead, and about half swam
out to the river on their own volition. Naman and crew began catching the
juvenile hatchery steelhead in the upper reach of the river as the
stragglers were forced out. They caught 1,636 juvenile hatchery steelhead,
finding that they had consumed 882 salmonid fry.

Using population estimates and predation rates, Naman estimated that 24,194
salmonid fry and 171,018 salmonid eggs were consumed by 2,302 residualized
hatchery steelhead in 21 days from Feb. 10 to March 2, 2007. He estimated
that 110,659 salmonid fry were eaten by 439,197 juvenile hatchery steelhead
in 30 days from March 28 to April 26, 2007.

Naman, now a fisheries biologist with the National Oceanic and Atmospheric
Administration Fisheries Service, wrote up the results of his Yurok study in
his master's thesis for Humboldt State University finalized over last
winter. It has been distributed widely over a Trinity River list server.



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http://www.trinityjournal.com/news/2009/0429/front_page/001p3_lg.jpg


Photos by PHIL NELSON 

"This study documents the highest rate of predation by hatchery salmonids on
naturally produced salmonids that has been reported," Naman states in his
thesis.

Reaction from a supervisor with the state Department of Fish and Game, which
operates the hatchery, is mixed.

"We do feel this study has merit, and it's an area that deserves more
attention," said Larry Hanson, senior biologist supervisor with the DFG's
Klamath/Trinity Program. "We don't necessarily agree with his conclusions."

For example, Hanson noted that the estimates for the daily population of
hatchery steelhead in the study area - and hence the extent of predation -
could have been high because, as acknowledged in Naman's report, one of two
antennas used to count 1,000 microchipped hatchery steelhead failed during
the study period.

During the spring high flow, "It would seem intuitive that a certain number
of those fish he believed residualized washed or migrated out of the study
reach," Hanson said.

However, in his report Naman lists several ways in which his predation
estimates are conservative, noting that almost half of the hatchery's
800,000 steelhead release was not included in the study.

He also noted that the hook and line method used to catch the steelhead may
have skewed the results toward individuals more likely to go after insects
than fish.

The hatchery, funded by the federal Bureau of Reclamation and operated by
the DFG, is meant to mitigate for the loss of fish habitat upstream from
Lewiston Dam. It releases Chinook and coho salmon as well as steelhead.

Naman suggests the agencies look into several issues regarding steelhead.

He notes that fishing regulations on the river from the Old Lewiston Bridge
to the dam are "fly only" and "catch and release only." These regulations
have no apparent biological justification, Naman stated, and angler harvest
of the hatchery steelhead could help eliminate those that stay in the river.

>From the DFG, Hanson said allowing anglers to keep steelhead in the upper
Trinity River would go against the hatchery's goals for returning adults.

"The department can't support that," he said.

Naman noted that each year a significant percentage of the 800,000 steelhead
released annually are on the small side - small enough that they have no
chance of returning as adults. In 2007, 175,210 small steelhead were
released, Naman said, and the stunted fish likely die or residualize in the
river to compete with naturally produced fish.

While Naman did not study the impact on wild fish from competition by
hatchery fish for food and habitat, he noted that other studies have, and
competition may be more harmful than predation.

"The end result of the competition may be dead naturally produced fish,"
Naman wrote, "which cannot be held in hand and counted as in this study."

Given the Trinity River Restoration Program goal of restoring naturally
produced salmonids, those goals "may be in conflict with the current
management regime of hatchery fish," Naman stated.

But Hanson noted that the hatchery is meant to mitigate for habitat lost due
to the dam, using the best science as to how many steelhead were produced in
that habitat. If neither the dam nor the hatchery existed, there would still
be predation by the natural steelhead, Hanson said. He acknowledged that the
dam does concentrate the fry.

Naman indicates in his report that the overlap of predator and prey is
occurring at a crucial time. He noted that wild Chinook and coho salmon fry
emerge from the gravel at the same time the 800,000 larger steelhead smolts
are released in the important wild spawning area, at a time when the river
is low and clear.

The consumed Chinook and coho salmon fry and eggs that would have hatched
make up 9 percent of production for the area during the study period, he
wrote.

Although it does not have regulatory authority over the hatchery, the
Trinity Management Council has discussed the issue. Hanson said the
management council has written the Bureau of Reclamation to see if fish
mitigation goals can be changed. There has not been a response from
Reclamation.

 

 

Byron Leydecker, JcT

Chair, Friends of Trinity River

PO Box 2327

Mill Valley, CA 94942-2327

415 383 4810 land

415 519 4810 cell

bwl3 at comcast.net

bleydecker at stanfordalumni.org (secondary)

http://www.fotr.org <http://fotr.org/>  

 

 

 

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