PORTLAND, Ore. (KOIN) – Researchers throughout the Northwest are working to help restore diminishing steelhead trout populations in the region and an Oregon State University scientist believes making adjustments at hatcheries could increase their chances of success.
Dr. Michael Blouin, a professor in the Department of Integrated Biology at Oregon State University, said his research shows that hatchery-raised steelhead give birth to offspring that are good at gaining size when they live in hatchery conditions, but they don’t survive well in streams.
He said like any animal raised in a controlled environment, hatchery steelhead are better adapted for captivity.
“In the wild, a little fish pops up out of the gravel and has to establish a territory, find food, which is scarce, not get eaten by predators. But in a hatchery, it’s in a big concrete box with 50,000 other fish, tons of food,” Blouin explained.
What’s happening, according to Blouin, is rapid evolution. Hatchery steelhead that are raised in a controlled environment where they’re free to be bold, eat as much as they want, and not hide from predators often grow quickly and survive in the wild due to their size. It’s their offspring, however, that do not return.
Blouin hypothesizes that when they spawn in the wild, steelhead pass on their genes to their offspring and the traits the parent had that made them unafraid and less capable of seeking out food sources can result in offspring starving to death or being eaten by predators. He said the research he recently published in PLOS One strongly supports this hypothesis.
“The problem with that is, hatchery managers have to limit the number of hatchery fish they can release because they’re worried about those fish that don’t get caught spawning in the wild and having negative genetic impacts,” Blouin said.
Blouin is trying to find a way to make hatchery fish more like wild fish. He said he and collaborators, including the Oregon Department of Fish and Wildlife, have already tried reducing the fat content in food, but found that had no effect. Now, they’ll move on to other small-scale experiments, like altering the density at which the fish are raised. In other words, they’ll allow them to mature with fewer fish surrounding them. They also plan to conduct an experiment where the fish are raised in water that’s constantly flowing, to see if that will increase the survival of their offspring.
Blouin said if they do find a treatment that has the effect they’re looking for, they’ll make it large enough to implement on a production scale and see if it has the same effect.
He said it could be years before they know what works. They’ll have to alter the conditions hatchery steelhead are raised in, allow them to spawn in the wild and see what the return of their offspring is.
Blouin said hatchery steelhead play a role in supporting wild steelhead populations. He said with the loss of habitat, hatcheries are necessary to the species’ survival. He said hatchery fish are sometimes added to wild steelhead populations to supplement them.