Maintenance of genetic variation in hatchery stocks of Atlantic salmon, Salmo salar L.: experiences from the River Bush, Northern Ireland

ABSTRACT

Abstract. An examination of biochemical-genetic variation at seven polymorphic loci was carried out among five year classes of wild Atlantic salmon, Salar L., in the R. Bush and in a hatchery strain derived from the wild population. Within some of the year classes, gene frequencies at several loci differed significantly between wild and artificially reared salmon. Highly significant temporal variation in gene frequencies was detected among successive year classes of the hatchery strain, while this was less significant among the wild salmon. Samples of wild salmon taken as 0+ and 1 + parr in the river showed no significant temporal variability in allelic frequencies. Heterozygosity levels among the wild and hatchery-reared salmon were comparable, averaging 0·185 and 0·176 respectively. The genetic variability of the artificially reared salmon is discussed in relation to numbers of broodstock and breeding regime used at the hatchery.