Finnish salmon resistant to Gyrodactylus salaris: a long-term study at fish farms

摘要: Abstract The occurrence of Gyrodactylus salaris on Baltic salmon ( Salmo salar ), sea trout S. trutta m. ) and brown lacustris was examined from 1984 to 1993 at 4 fish farms (A, B, C D) that produce smolts for stocking in northern Finland. No G. found the or trout, but it did occur 6–7 years D, prevalences infection being 9.5%, 17.7% 8.8% yearlings during time, respectively, less than 1.2% fingerlings B C. Only brood stock were infected farm A years. abundances increased second winter each year class highest spring before stocking. combination variables farm, water temperature, age other ectoparasites not suffice explain when studied by step-wise logistic regression analysis. It is suggested irregular factors such as a change intake system, transfers keeping wild are also important. present extensive data strongly support previons suggestions more resistant migrating into Atlantic Ocean.