GENETIC PROTEIN VARIATION AND NATURAL-SELECTION IN ATLANTIC SALMON (SALMO-SALAR L) PARR

The principal focus of this study was an examination of the relationship between diallelic variation at the MEP‐2* locus and growth and survival in Atlantic salmon parr. In addition, patterns of growth and survival among genotypes at the AAT‐I*, IDDH‐I* and ZDHP‐2* loci were also examined. Significant differences in growth were found among MEP‐2* genotypes, with *100/ 100 homozygotes largest in one of two independent comparisons and the *125/I25 homozygotes largest in the other. No growth differences were observed among genotypes at any other locus. Although no significant differences were found in survival among genotypes at any locus, results of joint analysis of the patterns of growth and survival among MEP‐2* genotypes were consistent with a model of positive size‐selective mortality. The demonstration of growth differences among MEP‐2* genotypes in parr and smolts may indicate an association between selection on this locus in fresh water and previously reported differences in sea‐age at maturity among MEP‐2* genotypes in Atlantic salmon. Copyright © 1991, Wiley Blackwell. All rights reserved