Wrasse on the lam


Wrasse are being caught and sold alive to salmon farms to combat salmon lice. Now wrasse are escaping from fish farms, which could have major implications for local fish populations, according to new research.

Many wrasse eat parasites and clean other fish. Salmon farms in Norway and Great Britain use various species of wrasse, especially Symphodus doderleini, to combat salmon lice. One of the most commonly used species is the corkwing wrasse.  But now wrasse are escaping from the Norwegian salmon farms. Well outside the farms, they spawn with fish from local populations, and as a result, their offspring will be hybrids between fish from the Skagerrak and Trøndelag, according to new research published in Royal Society Open Science.

“More than a third of the examined fish proved to be escapees or offspring from escapees”, says Ellika Faust, a doctoral student in conservation economics.