NOVEL CYPERMETHRIN FORMULATION FOR THE CONTROL OF SEA LICE ON SALMON (SALMO-SALAR)

A novel formulation of cypermethrin was applied as a bath treatment to Atlantic salmon infested with sea lice on a commercial fish farm on t he Isle of Skye, Scotland. Twenty 15 m x 15 m cages were treated with cypermethrin at a concentration of 5 mu g/litre sea water. The numbers of sea lice of all stages were recorded on five fish per cage before the treatment and one, seven and 16 days after treatment. Statisticall y significant reductions in the numbers of chalimus III and IV pre-adu lts and adults were recorded over the whole period; the average percen tage reductions at one and 16 days after treatment were 59 per cent an d 90 per cent (chalimus III and IV), 98 per cent and 95 per cent (pre- adults), and 99 per cent (adults), respectively.