Researchers explore ways to make hatchery steelhead more like wild fish

The Public Domain is a credit.

New research by Oregon State University shows that the offspring of steelhead trout that are raised in a hatchery are not as good as the offspring of wild fish.

The results suggest that it is possible to change rearing methods to produce fish that are more like wild steelhead, which could help them survive better and also allay concerns about them mixing with wild populations, said Michael Blouin, who led the study.

The hatcheries provide fish for harvest and to supplement wild stocks of an important species that is culturally and recreationally significant.

Like salmon, steelhead travel to the ocean as "smolts" and return to their natal streams to start a family. Eggs and fish are raised for a year and then released into the sea.

Blouin said that it is well established that fish that are raised in a hatchery make better brood stock than fish that are raised in a wild setting. When both fish are in the wild, fewer offspring are produced by the hatchery fish.

He said that hatcheries are inadvertently favoring genes that promote growth in the hatchery environment at a cost to survival in the wild.

The research suggests that there may be a way to modify the conditions of the hatchery so that they don't accidentally "select" for the traits that will be needed after release. Evolutionary biology refers to the process of passing beneficial genes on to improve a species' chance of survival.

The tradeoff is caused by genes disfavored in the wild.

A professor at Oregon State and a researcher at the Oregon Department of Fish and Wildlife looked at multiple full-sibling families of steelhead that were spawned either by two wild parents or two first-generation hatchery-raised parents.

Blouin said that all of the families' offspring were grown in artificial streams. The families of parents raised in the hatchery had lower survival in the streams. The tradeoff was apparent after just one generation of selection.

The number of adult offspring that survive to return from the sea is lower for salmon, trout and steelhead raised in hatcheries.

The better the odds of surviving in the ocean, the bigger the smolt is. There is no predator, lots of food and crowded. A natural stream is a low-food environment. Some juvenile fish might be prone to being eaten by predatory animals in the wild if they are allowed to take advantage of the hatchery and grow quickly.

Reducing the fat content of trout feed to make it more like a wild diet was looked at by the researchers, but there was no evidence that it would reduce the selection in the hatchery.

He said that researchers are testing whether other changes to standard rearing methods could be used to make fish more like wild fish.

Madeleine Wrey, James Skaar of the ODFW and Ronald Twibell of the Abernathy Fish Technology Center are some of the people who are involved in this project.

The Offspring of first-generation hatchery steelhead trout (Oncorhynchus mykiss) grow faster in the hatchery than offspring of wild fish, but survive worse in the wild. There is a journal called "journal.pone.0257407".

The journal contains information about the PLoS ONE.

Researchers explore ways to make hatchery steelhead more like wild fish.

The document is copyrighted. Any fair dealing for the purpose of private study or research cannot be reproduced without written permission. The content is not intended to be used for anything other than information purposes.