Hatchery Fish Often Fail in the Wild. Now We Might Know Why

Hakai Magazine –

Wild salmon are struggling to get their groove back. Along North America’s Pacific coast, salmon populations—already hit by overfishing—have been forced to dodge the Blob and hungry seals. For years, Canada has tried to help bolster the salmon population by releasing hatchery-raised juvenile fish, or smolts, into the wild.

Scientists know these hatchery smolts don’t do well in the wild—the fish tend to die younger than their wild brethren and reproduce less, but it’s unclear why.

In a recent study, however, researchers think they’ve hit upon a possible explanation. In two British Columbia streams, researchers caught coho salmon smolts that were making their way out to sea for the first time. Some of the fish had been born in hatcheries, while others were wild. Comparing the genetics of the hatchery- and wild-born smolts, the scientists found a huge difference between the two populations. But the changes weren’t so much in their genetics as in how their genes were regulated and expressed—their epigenetics.

Epigenetics is the physical and molecular processes that control how the instructions contained within DNA get expressed or turned into the proteins that affect day-to-day life. Often, epigenetics causes a gene to be expressed more or less frequently than it otherwise would. Everything from stress to chemicals to natural processes like puberty can cause epigenetic changes. Some of the changes are temporary or reversible, while others last forever.

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