Recent evidence in a paper soon to appear in Ecology Letters by Garant, Fleming, Einum & Bernatchez, however, indicates that, similarly to wild salmon, the male offspring of farm spawners may mature precociously in freshwater, and use their small size to sneak copulations, darting in next to the female's ovipositor at spawning and fertilizing large numbers of eggs.
In fact, such farm males are more successful at sneaking copulations, participating in more spawning events and having higher fertilization success than wild males. The rapid maturity, combined with higher growth rates and reproductive performance of male offspring of farm origin, will thus not only perpetuate, but speed the gene flow from farm fish into native salmon populations.
Ecology Letters