COMPARATIVE SUSCEPTIBILITY OF RAINBOW-TRO UT AND COHO SALMON TO ECTOPARASITES OF ECONOMIC IMPORTANCE

The comparative susceptibility of rainbow trout Oncorhynchus mykiss an d coho salmon Oncorhynchus kisutch to the parasites Caligus flexispina (Copepoda) and Ceratothoa gaudichaudii (Isopoda) was studied. The lan d-based salmon culture was carried out in 8 m(3) tanks with independen t and continuous sea water supply with two different densities and two replications at Bahia Metri (41 degrees 43'00 '' Lat. S., 72 degrees 36'30 '' Long. W). The copepod was found in 3 out of 4 tanks with rain bow trout with a prevalence from 14% to 83%, whereas a prevalence of 2 5% was found only in one tank with coho salmon. The isopod was present only in 2 of the 4 tanks with reared coho salmon with 28% and 29% of prevalence respectively. This indicates that C. gaudichaudii is an imp ortant parasite to the coho salmon and is unimportant to the trout. On the contrary, the coho salmon is more resistant to the copepod parasi te. This is the first record of C. flexispina in cultured salmonids fr om Chile.