Hatchery Fish Adapting To Captivity Within One Generation

Dec 29, 2011

If you want to make it in the animal kingdom you’ve got to adapt. Take our canine companions. At one point they were wolves. But over the course of thousands of years they realized that by hanging around people, life got a lot easier.

A new study out today suggests hatchery fish may be taking a lesson from lap dogs when it comes to adapting to life in captivity.

Mark Christie, a post-doctoral researcher at Oregon State University and an author, explains:

“It’s a bit like the process of turning wolves into dogs except in this case we have been able to document changes in reproductive success in a single generation.”

Christie wanted to better understand why hatchery fish don’t do as well in the wild. So he did genetic analysis on 12,700 hatchery-raised and wild steelhead in the Hood River in Oregon.

And using that genetic analysis, he was able to compare the numbers of offspring produced by fish born in captivity with wild fish brought into the hatchery to spawn. Christie found that in captivity, the hatchery-born fish had nearly double the reproductive success as wild fish. He says that shows that hatchery fish — even the first generation born to wild steelhead — are adapting to life in captivity – and quickly.

“That was what was so remarkable about this study,” Christie adds “was how quickly we saw those adaptations.”

Christie’s research was published in the journal of the Proceedings of the National Academy of Sciences.

The traits that make a fish do well in a tank with thousands of other fish don’t necessarily help that fish do well in an open river because the conditions are different. Christie says it’s not entirely clear which traits are helping hatchery fish out-compete wild fish in captivity.

“The next step is to figure out what exactly is under selection in the hatchery,” Christie says. “This study potentially points to a way to change hatcheries to create better hatchery fish or to figure out how to better implement hatcheries for conservation and management purposes.”

By “better hatchery fish,” Christie means hatchery fish that will survive better in the wild –- not in the hatchery.

Here’s one management suggestion from his research: give ‘em some room!

Christie looked at data collected over a 15-year period and an interesting tidbit arose: One year the number of fish in the hatchery was lower, meaning there were fewer fish per tank.

Christie found that those fish did much better when they were released into the wild than fish raised in more crowded years.

There’s been some controversy surrounding the use of hatcheries to supplement wild stocks of salmon and steelhead in the Northwest.

Several fish conservation groups have threatened to file a lawsuit against the Lower Elwha Klallam tribe on the Olympic Peninsula. The tribe is releasing non-native steelhead from its hatchery on the Elwha River in order to boost fish populations there.

If those hatchery fish are adapting to a life in captivity, some scientists worry that those fish may not only be ill-equipped to survive in the wild, but if they’re interbreeding with wild fish the result may be lap dogs, as opposed to wolves.