[env-trinity] Oregon State University on Hatchery Steelhead

Byron Leydecker bwl3 at comcast.net
Wed Oct 17 15:28:14 PDT 2007


STUDY CASTS DOUBTS ON HATCHERY FISH EFFORTS

Published: October 10, 2007

By Leah Weissman 

Pilot staff writer 

A 15-year study conducted by Oregon State University(OSU) reveals
hatchery-raised steelhead trout released in Hood River lose their ability to
reproduce in the wild at a drop-rate of about 40 percent per generation. 

Andrew Van Scoyk, hatchery manager of Rowdy Creek Fish Hatchery in Smith
River, said this study doesn't necessarily apply to every hatchery in
Oregon. 

"This is just one study on one river," Van Scoyk said. "There's a lot said
that doesn't relate to us. For instance, we only rear one generation at a
time." 

According to the research, offspring obtained strictly from farmed fish have
around half the reproductive fitness as fish reared in a hatchery for only a
single generation. 

Michael Blouin, an OSU associate professor of zoology 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." 

The decrease in reproductiveness is due to a combination of genetics and
natural selection, scientists administering the study said. The evolutionary
process selects certain characteristics suitable for fish living in a
protected environment such as a hatchery, but unsuitable for the
fish-eat-fish world of the wild. 

According to Van Scoyk, the major differences between steelhead at Rowdy
Creek Fish Hatchery and the hatchery steelhead released into Hood River are
the hereditary contrasts between the fish and the hatchery's mating
practices. 

"We never mate two hatchery fish," he said. "Whenever possible, we always
prefer to mate two wild fish. We also mate different sizes and ages of fish
to keep the gene pool mixed up. Finally, we clip the adipose fin (small
fleshy fin on the fish's back behind the dorsal fin) so we know, and
fisherman know, what fish are wild and what fish are farmed." 

The obvious physical difference makes it easy for the hatchery to
distinguish between wild and farmed fish when selecting different steelhead
to mate. The clipped fin is also a red flag to fishermen that this is a
farmed fish and should be caught. 

Earlier studies by OSU and the Oregon Department of Fish and Wildlife (ODFW)
mention that hatchery fish reared from wild stock have the potential to help
wild populations in the short run. 

"Our hatchery fish only make up about 30 percent of steelhead in Smith
River, so there's a higher chance of wild fish spawning with hatchery fish,
rather than two hatchery fish spawning and perpetuating the negative
traits," Van Scoyk said. "I think some of the data from this study are more
of a concern for hatcheries that take up a bigger proportion of the river." 

In the study, Blouin states that hatcheries have a place in fisheries
management. 

"The key issue is how to minimize their (hatcheries) impacts on wild
populations," he said. "Among other things, this study proves with no doubt
that wild fish and hatchery fish are not the same, despite their
appearances." 

Van Scoyk said he hopes people don't take this study too seriously and use
it to indict all hatcheries. 

"We want to improve the fish population, not harm it with bad genetics. The
Departments of Fish and Game has given us strict guidelines; we do our best
to stay within them."

 

 

Byron Leydecker

Friends of Trinity River, Chair

California Trout, Inc., Advisor

PO Box 2327

Mill Valley, CA 94942-2327

415 383 4810 

415 519 4810 cell

bwl3 at comcast.net

bleydecker at stanfordalumni.org

http://www.fotr.org

http://www.caltrout.org

 <http://www.fotr.org>  

 

 

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