The host transfer ability of Lepeophtheirus salmonis (Copepoda: Caligidae) from farmed Atlantic salmon, Salmo salar L.

The ability of mobile stages of Lepeophtheirus salmonis to transfer between salmon, Salmo salar L., hosts was examined by two methods. The first of these was the removal of certain stages on farmed fish, while the second comprised the placement of mobile lice on clean fish in the laboratory. In one-sea-winter farmed salmon, 63% of males and 52% of female lice transferred to new hosts over a period of 4 days. In laboratory trials on post-smolts, 61% of males and 69% of female lice transferred to new hosts over 3 days. In another experiment, free-swimming adult male lice were added to the tank, and 90% of these were found on fish after 24 h. Immigration of lice to fish in trial cages and the large proportion of lice transferring between fish in both laboratory and farm trials indicates that L. salmonis can transfer between hosts.