Abstract: Medetomidine or a salt thereof for use in controlling parasitic crustaceans, such as sea lice, on fish, e.g. salmon. A method of improving water flow into and out of a cage or net for fish farming, by providing said cage or net with a surface coating containing medetomidine or a salt thereof in an amount effective to reduce biofouling of said cage or net. The coating is capable of releasing medetomidine or the salt thereof into the water in the cage or net in an amount effective to reduce or prevent parasitic infestation of the fish in the cage or net.

Abstract: A combination of selected substances in paint to prevent the settlement and growth of different bio-fouling organisms with a reduced negative effect on the ecosystems compared to present methods. Useful substances include medetomidine with various copper and zinc formulations, tolylfluanide, diclofluanide, DIURON™ and IRGAROL™, or more general biocides such as SEANINE™ (4,5-dichloro-2-n-octyl-3(2H)-isothiazolone) or ECONEA™ (2-(p-chlorophenyl)-3-cyano-4-bromo-5-trifluoromethyl pyrrole).

Abstract: The use of an aromatic compound substituted with at least one heterocyclic amine and possibly additional substituents, such as medetomidine and clonidine, or a functionally analogous derivative thereof, as an agent for the inhibition of marine biofouling on a surface, by application thereon of said compound, is disclosed. Also a method for inhibition of marine biofouling on a surface by application of said compound is disclosed.