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Fall of Salmon Diversity

Genetic diversity among salmon in the Baltic Sea has fallen with the rise in fish farming, the Guardian reports.

Researchers from the Swedish University of Agricultural Sciences used a set of archival Atlantic salmon (Salmo salar L.) samples, collected for more than 100 years, to compare salmon from the 1920s and 1930s to modern salmon samples collected between 2010 and 2015. As they report in the Proceedings of the Royal Society B, the researchers found that the Atlantic salmon populations across the Baltic Sea have become more genetically homogenous. They traced the shift to the time when hatcheries began farming fish to stock the area to compensate fisheries following declines in native fish due to the effects of the hydropower industry.

"All these decisions [to rear fish] were taken in the 1950s and 60s … but since then, they've never been reviewed scientifically. Maybe it's time to actually have a more scientific base," first author Johan Östergren of the Swedish University of Agricultural Sciences tells the Guardian.