[env-trinity] Hatchery Fish May Hurt Efforts To Sustain Wild Salmon Runs - Science Daily - June 10, 2009

[Seth Naman]

The paper is attached if you don't already have it.

Thomas Weseloh wrote:
>
>
>   Hatchery Fish May Hurt Efforts To Sustain Wild Salmon Runs
>
> */ScienceDaily    /*            
>
> June 10, 2009
>
> ** 
> <http://www.sciencedaily.com/images/2009/06/090610091224-large.jpg>/*Steelhead 
> trout return to spawn.*//* (Credit: John McMillan)*/**
>
> Steelhead trout that are originally bred in hatcheries are so 
> genetically impaired that, even if they survive and reproduce in the 
> wild, their offspring will also be significantly less successful at 
> reproducing, according to a new study published today by researchers 
> from Oregon State University.
>
> The poor reproductive fitness - the ability to survive and reproduce - 
> of the wild-born offspring of hatchery fish means that adding hatchery 
> fish to wild populations may ultimately be hurting efforts to sustain 
> those wild runs, scientists said.
>
> The study found that a fish born in the wild as the offspring of two 
> hatchery-reared steelhead averaged only 37 percent the reproductive 
> fitness of a fish with two wild parents, and 87 percent the fitness if 
> one parent was wild and one was from a hatchery. Most importantly, 
> these differences were still detectable after a full generation of 
> natural selection in the wild.
>
> The effect of hatcheries on reproductive fitness in succeeding 
> generations had been predicted in theory, experts say, but until now 
> had never been demonstrated in actual field experiments.
>
> "If anyone ever had any doubts about the genetic differences between 
> hatchery and wild fish, the data are now pretty clear," said Michael 
> Blouin, an OSU professor of zoology. "The effect is so strong that it 
> carries over into the first wild-born generation. Even if fish are 
> born in the wild and survive to reproduce, those adults that had 
> hatchery parents still produce substantially fewer surviving offspring 
> than those with wild parents. That's pretty remarkable."
>
> An earlier report, published in 2007 in the journal Science, had 
> already shown that hatchery fish that migrate to the ocean and return 
> to spawn leave far fewer offspring than their wild relatives. The 
> newest findings suggest the problem does not end there, but carries 
> over into their wild-born descendants.
>
> The implication, Blouin said, is that hatchery salmonids - many of 
> which do survive to reproduce in the wild- could be gradually reducing 
> the fitness of the wild populations with which they interbreed. Those 
> hatchery fish provide one more hurdle to overcome in the goal of 
> sustaining wild runs, along with problems caused by dams, loss or 
> degradation of habitat, pollution, overfishing and other causes.
>
> Aside from weakening the wild gene pool, the release of captive-bred 
> fish also raises the risk of introducing diseases and increasing 
> competition for limited resources, the report noted.
>
> This research, which was just published in Biology Letters, was 
> supported by grants from the Bonneville Power Administration and the 
> Oregon Department of Fish & Wildlife. It was based on years of genetic 
> analysis of thousands of steelhead trout in Oregon's Hood River, in 
> field work dating back to 1991. Scientists have been able to 
> genetically "fingerprint" three generations of returning fish to 
> determine who their parents were, and whether or not they were wild or 
> hatchery fish.
>
> The underlying problem, experts say, is Darwinian natural selection.
>
> Fish that do well in the safe, quiet world of the hatcheries are 
> selected to be different than those that do well in a much more 
> hostile and predatory real-world environment. Using wild fish as brood 
> stock each year should lessen the problem, but it was just that type 
> of hatchery fish that were used in the Hood River study. This 
> demonstrates that even a single generation of hatchery culture can 
> still have strong effects.
>
> Although this study was done with steelhead trout, it would be 
> reasonable to extrapolate its results to other salmonids, researchers 
> said. It's less clear what the findings mean to the many other species 
> that are now being bred in captivity in efforts to help wild 
> populations recover, Blouin said, but it's possible that similar 
> effects could be found.
>
> Captive breeding is now a cornerstone of recovery efforts by 
> conservation programs for many threatened or endangered species, the 
> researchers noted in their report. Thousands of species may require 
> captive breeding to prevent their extinction in the next 200 years - 
> which makes it particularly important to find out if such programs 
> will ultimately work. This study raises doubts.
>
> "The message should be clear," the researchers wrote in their report's 
> conclusion. "Captive breeding for reintroduction or supplementation 
> can have a serious, long-term downside in some taxa, and so should not 
> be considered as a panacea for the recovery of all endangered 
> populations."  
>
> *###*
>
>  
>
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-- 
Seth Naman
Fisheries Biologist
NOAA Fisheries
Southwest Region
1655 Heindon Rd.
Arcata, CA 95521
707-825-5180
fax: 707-825-4840

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