GENETIC-VARIATION IN GROWTH-RATE OF ATLANTIC SALMON WITH DIFFERENT TRYPSIN-LIKE ISOZYME PATTERNS

The growth rates of three different year-classes (1984, 1985 and 1987) of Atlantic salmon (Salmo salar) were studied using trypsin-like isozyme pattern in the pyloric caeca as a biological genetic marker. The fish with the homozygote variant TRP-2(92/92) and with the heterozygote variant TRP-2(92/100) had higher average weight than those with the genotypes which did not possess the variant TRP-2(92). The difference in weight between the two groups (with and without TRP-2(92) variant) was significant from smolt until the end of the experiment in autumn of the first sea-year (1984 year-class) and until spring in the second sea-year (1985 year-class). The difference was about 30%, and decreased to 10% at maturation. The specific growth rate was critical during the first sea-year. The fish with the allele TRP-2(92) showed the advantage of faster growth in the first sea-year, especially during winter time. With the covariation of significant difference in weight (until the autumn in the second sea-year) among different families, higher production of food fish of at least 20% could be possible at the time of slaughter during the second sea-year with the use of a selective breeding programme based either on trypsin-like isozyme pattern and family or on the isozyme pattern of individuals. The effects of selection by using the variant TRP-2(92) could be observed within the period of the generation selected.