The effect of removing a natural migration barrier on a previously isolated population of Brown trout (Salmon trutta L.) – Kvåsfossen, Norway.

In the years of 1970s and 1980s acidic rain threatened coastal freshwater fish populations in European rivers. Several fish populations in western and southern Norway were particularly affected including the Norwegian brown trout (Salmon trutta L.). Liming of lakes and rivers has had positive effects on re-establishment of fish populations in many Norwegian rivers. Migration barriers, natural or man-made is another challenge for anadromous coastal fish populations. By completely or partially isolating upstream populations from downstream migration, these barriers hinder gene flow and thereby reduce genetic diversity in the upstream populations. In 2014 a fish ladder was built in Kvåsfossen …