The enzyme gene variation of ten Finnish rainbow trout strains and the relation between growth rate and mean heterozygosity

Abstract

The electrophoretic survey of 10 rainbow trout ( Salmo gairdneri Richardson) strains reared in Finland was made in connection with a simultaneous analysis of the growth rate of the strains. Five of the strains were from a State Fish Culture Station and the other five from commercial fish farms. Nine enzyme systems and 20 loci were examined. Eight loci were polymorphic. The genetic variation found was at about the same level as in earlier rainbow trout studies. Thus, Finnish rainbow trout strains have probably not lost much genetic variation since they were imported from the U.S.A. Genetically, the most distinct strain was the autumn spawning one. The genetic distances between the commercial strains were smaller than between the strains of the State Fish Culture Station. The genetic variation and the growth rate were greater in commercial strains than in the State strains, which have been kept more isolated from each other. In the nine spring spawning strains the correlation between the mean heterozygosity ( H) and average growth rate in sea water was 0.62, between H and growth rate in fresh water 0.59, and between H and the average weight 0.54. When only eight stocks of the same origin were included, the corresponding correlations were +0.83 ( P < 0.05), +0.70 ( P < 0.1) and +0.76 ( P < 0.05), and the correlation between H and the variation in weight was −0.66 ( P < 0.1).