Hatchery Rearing Can Change Fish Genetics

By on February 23, 2016
Steelhead trout. (Credit: Cacophony via Creative Commons 2.5)

For years, fisheries biologists have suspected that fish raised in hatcheries were not as fit for survival following release as their wild counterparts. After a recent study led by scientists at Oregon State University, they now have proof that their suspicions on fish genetics were correct.

The investigation focused on two sets of offspring from steelhead trout, each raised in similar conditions. One set had parents that were raised in hatcheries from Oregon’s Hood River. The other set had one parent that had been raised in a hatchery and another that had been reared in the wild.

After seeing each set of offspring grow up, the researchers began to compare the genetics of the second-generation hatchery fish with those from the trout that had at least one wild parent.

The results were quite clear. Fish that had genes from hatchery-raised parents differed in the activity of more than 700 genes when compared to offspring that had a wild parent. Since the conditions in which each set of offspring was brought up were identical, scientists note that the difference must be something going on solely in the fishes’ genes.

But whatever precise genetic differences there are between the two sets of fish is still not completely clear to the researchers. And it isn’t yet evident what specific traits are being selected for or what environmental factors could be helping to drive the changes.

The goal for the scientists now is to pinpoint what factors, in addition to where their parents come from, are influencing the genetic makeups of fish raised in hatcheries. If they can nail those down, then the researchers would like to help hatcheries managers make changes that could bring about more robust fish offspring from hatcheries.

For example, overcrowded conditions could be impacting changes in DNA and making fish more docile. If that were proven to be the case, then hatcheries managers could design holding tanks with more room for fish to grow and move around.

Results of the research underscore the need for action because of the short amount of time, just one generation, that the genetic changes need to take hold.

They may also support another hypothesis that some scientists have relating to the long-term survivability of hatchery-raised fish via the breeding that can occur between wild fish and those raised in artificial environments. The worry is that the interbreeding of the two strains of fish could result in watered-down genetic material that could make fish less competitive for survival in the long term.

Full results of the study are published online in the open-access journal Evolutionary Applications. In them, researchers note that there is a limited amount of data on the subject available. More research is needed, they say, to make more concrete generalizations about the fitness of fish reared in hatcheries.

The study was funded in part by contracts from the Bonneville Power Administration, as well as by the Oregon Department of Fish and Wildlife.

Top image: Steelhead trout. (Credit: Cacophony via Creative Commons 2.5)

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