Artificial settlement of sea lice, caligus rogercresseyi boxshall & bravo, 2000 (copepoda, caligidae), on tissues of fish used as substrate

Caligus rogercresseyi is the main ectoparasitic copepod affecting salmon and trout farming in Chile. The aim of this study was to evaluate under laboratory conditions the ability of copepodids of C. rogercresseyi to settle on fin, scale, and skin tissues taken from a wild host, the rock cod (Eleginops maclovinus) and an exotic host (Oncorhynchus mykiss), and evaluate the effects of inductors, such as conditioned water and fish mucus, on the process. The assessment was carried out simultaneously for each host and inductor, using a single pool of larvae (N = 1800). Three replicates per treatment were done and the settlement as well as the development stage of the frontal filament were recorded after 24 h. A total of 341 copepodids were able to settle on the different tissues and hosts. The host showing the higher settlement was E. maclovinus (N = 215; 23.9%) compared to O. mykiss (N = 126; 14%); the tissue showing the higher number of settled copepodids was the skin (N = 126; 48.4%), followed by fin (N = 140; 41.1%) and scales (N = 36; 10.5%). Regarding inductors, neither conditioned water (N = 112; 32.8%) nor mucus (N = 113; 33.1%) showed significant differences with the control without inductor (N = 116; 34%). Inductors did not have a significant effect on the development of the frontal filament, neither for E. maclovinus, nor for O. mykiss tissues, thus suggesting the tissues used were able to induce a positive response on these processes. This is the first work reporting a successful settlement of a species of sea louse in tissue extracted from fish.