Genetic correlations between survival of Atlantic salmon in challenge and field tests

Four sub-samples of 171 full-sib groups of Atlantic salmon presmolts (the offspring of 96 sires and 171 darns) were tested for survival after challenge with the pathogenic bacteria Areomonas salmonicida, Vibrio salmonicida, Vibrio anguillarum and the viral disease Infectious Salmon Anaemia (ISA). Another sub-sample of 123 of the full-sib groups was tested as postsmolts at a marine test-site (field test) where infection with A. salmonicida prevailed causing high mortality during a two-month summer period. A full-sib group mean MINQUE model was used to estimate the variance and covariance components for survival in each test environment. Estimated heritabilities on the underlying liability scale for survival in the challenge test with A. salmonicida was 0.53 (at 50% survival) and in the field test 0.38 (at 65% survival). The genetic correlation between survival in the two tests was 0.95. Thus, the results give good prospects for genetic improvement of resistance to furunculosis when survival data from challenge tests of presmolts are used as the selection criterion. The results also indicate a positive genetic correlation between resistance to each of the bacterial diseases, but a weak negative genetic correlation between resistance to the viral disease ISA. and resistance to each of the bacterial diseases. (C) 1997 Elsevier Science B.V.