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Flaw limits captive fish, study says
Hatchery-bred fish have long sliced through Northwest rivers along with wild fish, raising the question: What's the difference?
An intensive study of steelhead in the Hood River has verified the difference. Fish bred for generations in hatcheries do little besides fill fishing nets, because they have slim hope of producing young that reach adulthood.
The finding, by Oregon State University and federal researchers, stands out because the difference between hatchery and wild fish lies at the center of debates over salmon in the Northwest, where more than a half-billion dollars annually goes to efforts for the recovery of the fish. While many scientists contend wild fish are vital to the future of their species, other groups argue that wild fish do not need protection if hatchery fish are plentiful.
Hatchery fish abound in the Columbia River system, and the research confirms that captive fish lose the instincts and other traits that let wild fish thrive.
Typical hatchery steelhead produced 60 percent to 90 percent fewer offspring that last long enough to become adults than wild steelhead, according to the OSU study just published in the journal Conservation Biology.
By breeding fish over and over in hatcheries, "we've essentially created a fish version of white lab mice," said Michael Blouin, an associate professor of zoology at Oregon State. "They are well adapted to life in the hatchery but do not perpetuate themselves in a wild environment as successfully as native-born fish."
The study shows that the longer fish spend in hatcheries, the poorer they will do in the wild, Blouin said.
Nine of every 10 hatchery programs in the Northwest turn out captive-bred fish that threaten to mix with wild fish, spreading their inferior traits.
"They certainly don't do well in the wild and can have significant detrimental effects on wild fish," said Rod French, a district fish biologist with the Oregon Department of Fish and Wildlife who is familiar with the study.
Biologists said the results may bear out with other species, among them coho salmon.
The good news is the study also found that much better results come from the newer strategy of taking eggs from local wild fish, hatching and raising the young in captivity, and then turning them loose.
The strategy attempts to protect the fish during their most vulnerable age but set them free before they morph into creatures of captivity. The study found that these fish do about as well, or possibly better, than wild fish when it comes to producing offspring.
It means the few hatcheries that have adopted the "supplementation" approach can boost wild fish populations without diluting their fitness.
Hatcheries increasingly are shifting to the new supplementation strategy, especially where they are trying to resurrect salmon species that are sinking toward extinction.
Fish factories
Far more hatcheries serve as fish factories, using salmon stocks bred in captivity to churn out large numbers for fishermen to catch. Many were built to stand in for important commercial salmon runs lost to dams built on the Columbia and other rivers.
Fish turned out of those hatcheries are not meant to recover the populations, but biologists have grown increasingly concerned that they also may compete with and interbreed with wild fish.
The new study looked only at steelhead that in the past 15 years have returned from the ocean to the Hood River.
The river was long stocked with domesticated hatchery fish from other parts of Oregon and Washington. In the 1990s, state biologists phased out that stocking program and instead switched to the new supplementation approach that hatches wild fish in captivity and then releases them.
State biologists collected and saved scales from fish swimming up the river since 1991. OSU scientists obtained DNA from the scales, which allowed them to trace the history of each fish and determine whether it was wild or came from a hatchery.
Faring poorly
The results showed that domesticated hatchery fish in 1991 fared very poorly compared to wild fish, but the fish kept only briefly in the Parkdale fish hatchery did about as well as wild fish.
It makes clear that traditional hatchery fish will not rebuild wild populations, said Mark Chilcote, a conservation biologist with the Oregon Department of Fish and Wildlife.
But the fish held briefly in hatcheries can help.
However, biologists caution that it is not clear whether they can hold successive generations of fish in hatcheries the same way without altering their character. Other studies suggest that hatchery fish lose about 20 percent of their fitness each generation they spend in a hatchery compared to wild fish.
Jim Lichatowich, a fisheries biologist and critic of hatcheries, said the findings are good news because it suggests a method of boosting wild populations, at least briefly. But he cautioned against viewing it as a cure-all because salmon also need healthy habitat.
Michael Milstein: 503-294-7689; michaelmilstein@news.oregonian.com
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