New research has found that a hatchery using wild salmon to spawn the next generation can help rebuild endangered salmon runs without passing on genetic problems that threaten future returns.
The study, published Monday in the online edition of the scientific journal Molecular Ecology, contrasts earlier research suggesting that hatcheries themselves genetically select for fish that go on to fail once they are released into the wild.
Researchers from the Columbia River Intertribal Fish Commission and the Nez Perce Tribe tracked an endangered run of chinook salmon in Johnson Creek in the Salmon River Basin in Idaho from 1998 through 2010 more than two full generations. The commission and the Nez Perce Tribe have long been strong advocates for using hatcheries to rebuild endangered salmon runs, a practice questioned by some scientists.
Genetic sampling from 7,726 adult fish returning to spawn showed that fish born and raised in the hatchery from parents taken from the wild produced adult fish that returned from the ocean at a higher rate — an average of 4.69 times higher than fish spawned naturally in the river. When those returning fish spawned naturally in the river, they produced offspring that returned at an average rate of 1.32 times higher over two brood years. They also found that male fish raised in hatcheries typically had a lower rate of success reproducing than wild males.
"This helps us realize that supplementation programs can be effective at boosting populations that are endangered while having very limited genetic impact on wild populations," said co-author Shawn Narum, lead geneticist for the commission.
Hatcheries have long been used to make up for lost habitat, such as dams blocking access to spawning grounds, and the vast majority of salmon in the Columbia basin are born in hatcheries. But it eventually became clear that traditional hatchery practices were one of the problems that have led to 13 runs of salmon and steelhead being protected by the Endangered Species List. While scientists have urged practices to change, change has been slow, and hatcheries producing salmon only from wild brood stock are rare. It is more difficult and more expensive to go into the wild to collect fish for spawning than it is to wait for fish to swim into the hatchery.
David Noakes, professor of fisheries at Oregon State University and senior scientist at the Oregon Hatchery Research Center, was not part of the study. He said the research was well done and published in a highly respected journal.
He noted that earlier research suggesting hatcheries produce inferior fish was done with a different species, steelhead, which could account for the different findings. Steelhead do not all die after spawning, and in nature spend two years in rivers before migrating to the ocean to mature. However, when raised in hatcheries, they are fed heavily to speed up their growth so they can be released after only one year. Unlike chinook salmon, many steelhead never go to the ocean, but remain in rivers as rainbow trout.
Another factor could be that fish bred in hatcheries do not get to choose their mates, the way animals from fruit flies to humans do in real life, he added.
"It is important to understand, and they make this clear in the study, that hatcheries are a tool that can be used for a variety of purposes," Noakes said. "They are not a solution, they are a tool."