Wild salmons are quite different from their counterparts raised in hatcheries on farms, having as many as 736 genetic variations. Researchers at Oregon State University in collaboration with the Oregon Department of Fisheries and Wildlife conducted a study to throw light on these differences, which have long been theorized to exist.

During the study, published Wednesday in Nature Communications, the researchers found DNA evidence to corroborate their claim as they compared the offspring of first-generation salmon raised in a hatchery with those in the wild.

The main difference between the two is on the reproduction and survival front. Citing an example, the researchers said if the salmon hatched on farms are released to the wild, they have a far tougher time reproducing as compared to their indigenous cousins.

Mark Christie, lead author of the study, said, “We observed that a large number of genes were involved in pathways related to wound healing, immunity, and metabolism, and this is consistent with the idea that the earliest stages of domestication may involve adapting to highly crowded conditions”.

Michael Blouin, an author of the study, said their findings settle to quite an extent the question of whether hatchery fish can have genetic variations after just a single generation of domestication.

What is more important is that this study is a step in the direction of trying to figure out which traits are under strong selection in the hatchery, and what hatchery conditions exacerbate that selection.

“A fish hatchery is a very artificial environment that causes strong natural selection pressures”, Blouin explained in a statement.

The difference on the survival front could be due to the fact that in artificial fish farms, salmons are packed gill-to-gill. Such conditions make the salmon in hatcheries vulnerable to disease and contamination and, thus, the risk to survival.