Individual variation in sea lice (Lepeophtheirus salmonis) infection on Atlantic salmon (Salmo salar)

The same individually tagged Atlantic salmon were subject to two separate challenges with the sea louse, Lepeophtheirus salmonis, in a single tank. A multiple regression model was used to investigate the potential influence of individual variation in density of lice in challenge 1, weight of fish in challenge 2 and family of origin, on the observed variation in intensity of lice in challenge 2. The model gave an overall R-2=0.165, P<0.003. Decomposition indicated that the only variable exhibiting a significant influence on the observed variation in individual variation in intensity of lice in the second challenge was fish weight (P<0.006). These data demonstrate that an individuals relative infection level in the first challenge was a poor predictor of its relative infection in the second challenge. (C) 2004 Elsevier B.V. All rights reserved.