A novel lice control method: photochemical treatment (Photolice)

Abstract

Control of salmon lice has long been the biggest challenge for the further development of a sustainable industry. Preventive measures are expected to play an increasing role, but experience suggests that drug treatment will still be an important tool in an effective lice strategy. Today's control options are limited by unwanted environmental effects or resistance issues linked to the use of chemicals. This project has tested whether light-activated chemicals used in e.g. human cancer medicine could be an effective and environmentally friendly treatment method against salmon lice. The project consisted of three parts, which first examined the direct effect of substances on salmon lice (screening phase), after which selected substances were tested on lice-infected fish and finally on organisms from the environment around the cage. Nine different compounds were tested, where three of the tested compounds induced mortality when applied directly to salmon lice but did not induce loss of salmon lice when applied to infected fish. The tested compounds had no negative effects on fish welfare, nor did they induce mortality or change the behavior of rock-pool shrimps, which were used as an example of an organism that might be affected. We conclude that the use of photoactivated compounds may be possible to eliminate salmon lice from fish in aquaculture environments, but further studies are necessary.

A novel lice control method: photochemical treatment (Photolice)