New study: time to review the release of farmed salmon

The release of farmed salmon has affected wild salmon stocks, according to a new study from the Swedish University of Agricultural Sciences (SLU). Over the years, the spawning grounds of several wild salmon have disappeared as a result of hydropower construction, something that they have tried to compensate for by growing salmon in controlled environments – and then putting them out into the wild. Now scientists worry about how the farmed salmon has affected the DNA structure of the wild salmon. Johan Östergren, is one of the main authors of the study:

“There are clearly genetic risks with salmon releases, and given that, the current model for releases should be reviewed. There is an obvious risk that the increased genetic confusion could have long-term negative consequences for wild salmon stocks,” he says.

In their study, Östergren and his colleagues have investigated the genetic structure of 13 different salmon stocks in the Baltic Sea. They have made analyses on salmon mountains that have been compared with mountains from the 1920s and 30s from the same water. The fact that the unique gene set has now changed in different species of wild salmon may make it more difficult for the salmon to survive future environmental changes, the authors say.

“By adjusting the release quantities, we can reduce the risks of mismigration and unwanted genetic influence on wild salmon populations,” says Johan Östergren.

He is now calling for a common strategy from all Baltic Sea countries when it comes to salmon release, where the place and time of releases should be based on scientific guidelines.

– In addition, there should be flexibility so that the extent of the conditions can be adapted to the prevailing fishing pressures in the sea and along the coast.

Read the full study here.