Hatchery life changes fish genetics, Oregon study finds

Hatchery steelhead

Steelhead writhe in a hatchery. A new study used steelhead from the Hood River to determine that hatchery life changes fish at the genetic level.

(Oregonian file photo)

A new study out of Oregon State University lays to rest the debate over whether hatchery life changes fish at the genetic level.

It does - and the changes happen at an astoundingly rapid pace.

The study, published Wednesday in the journal Nature Communications, finds that after only one generation of domestication, the DNA of hatchery steelhead trout is substantially different from the DNA of steelhead whose parents were wild.

In other words, fish begin evolving to suit their habitat in just a single generation.

"We're showing that, at the DNA level, hatchery and wild fish pass on something different to their offspring," said Michael Blouin, an OSU researcher who served as principal investigator on the study.

Blouin said the findings prove some scientist' long-held suspicions about why the offspring of hatchery-raised fish are less likely to survive in the wild than the offspring of wild fish.

Several studies have found that that hatchery-raised fish and wild fish differ in their survival and reproductive success, but it remained unclear whether learned behavioral changes or DNA-level differences were behind the phenomena.

The research by Blouin and his team makes it clear that genetics plays a role.

The team conducted their study using wild and hatchery-raised steelhead from the Hood River. They bred the fish, then raised their offspring - batches of fertilized eggs with two wild parents, with two hatchery-raised parents, and with one wild parent and one parent from a hatchery - in identical conditions.

When they were done, they compared the genetics of each class of fish. Fish with hatchery-raised parents differed in the activity of more than 700 genes when compared to fish with wild parents. The fish had all been reared in the same environment, and their parents had been caught in the same water.

"The only difference," Blouin said, "is who their parents were."

It's not clear what traits are being selected for, nor what environmental factors are driving the evolution. But if scientists can pinpoint those details, hatchery managers could make changes at their facilities to produce hatchery fish that are as genetically-similar as possible to their wild counterparts.

For example, if overcrowded conditions in hatcheries were prompting a DNA change that makes fish more docile, hatchery managers could feasibly design hatcheries with more room for fish to grow in hopes of avoiding the DNA change.

That could do much to alleviate the concerns over whether our hatchery system is making it harder for wild fish to survive. Although the system is designed to prevent interbreeding, some hatchery-raised fish inevitably spawn with wild fish. Some fish advocates worry that over time, interbreeding leads to genetic changes that make wild fish less fit to survive in their environment.

"There's a potential to make hatchery fish that end up more like wild fish, and then everybody's happier," Blouin said.

--Kelly House