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Research proves wild fish breed better than hatchery species

OREGAN - A 15-year analysis of spawning steelhead in one Oregon fishery has proved that fish released from hatcheries are not as prolific as their wild cousins.

The research, conducted by Oregon State University (OSU) and the Oregon Department of Fish and Wildlife, shows that when hatchery-produced fish migrate to the ocean and then return to spawn in natural habitats, they produce far fewer offspring than their wild relatives.

The study used DNA tracking technology to monitor fish breeding in the Hood River. It showed that traditional hatchery steelhead produced 60-90 per cent fewer surviving adult offspring than wild steelhead.

However, the research also confirmed that fish from modern “supplementation” hatcheries, which begin with eggs from native wild fish, can be as successful in reproductive performance as wild steelhead.

The findings, published in the online journal Conservation Biology, provide compelling evidence to support what fish experts have suspected for some time - that fish from traditional hatchery operations have a much-reduced ability to reproduce and sustain themselves in the wild.

“We’ve essentially created a fish version of white lab mice,” said Michael Blouin, an associate professor of zoology at OSU. “Theses fish are well-adapted to life in the hatchery, but do not perpetuate themselves in a wild environment as successfully as native-born fish. The good news, however, is that reducing the number of generations a stock is passed through the hatchery can greatly increase the fitness of that stock in its natural habitat,” he explained.

Role change
The role of hatcheries is changing and many are now geared to produce species to bolster dwindling wild populations.

The work at OSU suggests that first-generation hatchery fish can be used to provide a one-time boost to a wild population without apparent damage to the genetics of the wild stock. But, whether this policy can continue to be beneficial on a long-term basis remains unclear.

Professor Blouin said that the offspring of hatchery fish actually made better “domesticated” fish in the hatchery environment, because inadvertent selection for traits like a less aggressive temperament produced stocks that had high egg-to-smolt survival in the hatchery situation.

However, the genetic characteristics that make for good hatchery fish work against the offspring of those animals when they are born into a competitive, predatory wild environment.

The techniques used in supplementation hatcheries – use of local, wild-born fish for eggs – have been designed to minimize the hatchery traits. And from these studies it appears policy can work - on a short-term basis.

“By tracing the lineage of those fish, we’ve shown pretty clearly that fish from traditional hatcheries do not reproduce as successfully as wild fish, and thus could potentially drag down the health of wild populations by interbreeding with them,” Blouin said. “But in places where we need a short-term boost to a wild population, it also appears that supplementation hatcheries may work well and not cause significant problems.”

Further Reading

- You can view the published article (pdf) by clicking here.