an unusual problem is plaguing the Norwegian rivers. Wild salmon returning to native habitats for spawning face an unexpected threat: salmon escapees that are either bred in fish farms or raised in special metal tanks with artificial lighting to speed up reproduction. These escapees are also vaccinated against infections and thus have an advantage over wild salmons.
Geneticists fear that the wild salmon population could be decimated by the booming aquaculture practices in Europe and North America, unless forceful control measures are brought in. Stated Lars Petter Hansen, scientist at the Norwegian Institute for Nature Research, "The heavy numbers of escaped farm fish make us believe that the genetic constitution of wild stocks will change so that they will be less adapted to their local habitats."