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

frankemerson@redshift.com frankemerson at redshift.com
Fri May 1 10:54:38 PDT 2009


I am not very impressed with the conclusions of this study. If there was a
natural healthy population of steelead in comparable numbers as the
hatchery numbers there would be similar predation. The eggs being consumed
are presumably free floaters which is natural, fry predation is normal.
The student had a hook and line catch method? Sounds like a great gig if
you can get it.

Predation could likely be reduced greatly if the hatchery steelhead were
released after the spring restoration flows have peaked. As an additional
benefit the higher flow would reduce residualization and cause better
Ocean survival of hatchery smolts due to more robust size.

If it were not for brown trout in upper river there would likely be even
more residnet trout in the natural spawning section.

Frank Emerson
CRSA

> 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.
>
>
>
>  <javascript:openimage('001p1_xlg.jpg',1024,444)>
> 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.
>
>
>
>  <javascript:openimage('001p2_xlg.jpg',838,1024)>
> 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.
>
>
>
>  <javascript:openimage('001p3_xlg.jpg',876,1024)>
> 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
>
>  <mailto:bwl3 at comcast.net> bwl3 at comcast.net
>
>  <mailto:bleydecker at stanfordalumni.org> bleydecker at stanfordalumni.org
> (secondary)
>
>  <http://fotr.org/> http://www.fotr.org
>
>
>
>
>
>
>
> _______________________________________________
> env-trinity mailing list
> env-trinity at velocipede.dcn.davis.ca.us
> http://www2.dcn.org/mailman/listinfo/env-trinity
>



More information about the env-trinity mailing list