Prospects for a genetic management strategy to control Gyrodactylus salaris infection in wild Atlantic salmon (Salmo salar) stocks

We estimated additive genetic variation and heritability of survival after Gyrodactylus salaris infection from survival records in a pedigreed family material of wild Atlantic salmon (Salmo salar) in a controlled challenge test. We used a statistical model that distinguishes between survival time for the fish that died and the ability to survive the entire test as two separate traits. Eleven of the 49 full-sib families suffered 100% mortality, 15 families had between 10% and 25% survival, and the four least affected families had survival rates between 36% and 48%. Estimated heritability of sur- vival on the liability scale was 0.32 ± 0.10. Time until death for fish that died during the test and the ability to survive the entire test were not expressions of the same genetic trait. Simply selecting survivors as parents for the next generation is expected to more than double the overall survival rate in only one generation, given similar exposure to the parasite. Im- proving the genetic capacity to survive the infection will probably not eradicate the parasite, but when used as a disease control measure, such improvement may contain the infection at a level where the parasite ceases to be a major problem. Resume ´ : Nous estimons la variation genetique additive et l'heritabilitede la survie apres une infection a Gyrodactylus sa- laris apartir des donnees de survie dans un echantillon provenant d'une famille d'ascendance connue de saumons atlanti- ques (Salmo salar) sauvages dans un test controled'exposition au parasite. Nous utilisons un modele statistique qui discrimine entre la duree de survie des poissons qui sont morts et la capacitede survivre a l'ensemble du test comme deux