Amount and distribution of biochemical‐genetic variation among wild populations and a hatchery stock of Atlantic salmon, Salmo salar L., from north‐east Ireland

Abstract

Tissue samples from a total of 617 Atlantic salmon from seven locations in north‐east Ireland were electrophoretically examined for genetic variation at 28 enzyme loci. Patterns of allelic variation at eight polymorphic loci indicated the existence of genetic differentiation within, as well as among, river systems. This suggests the presence of localized genetically differentiated populations of salmon in N. Ireland. Temporal variation in allelic frequencies was tested among three year classes of wild R. Bush salmon and found to be insignificant compared to the spatial variation. Examination of equivalent year classes of R. Bush hatchery‐reared salmon displayed significant temporal variation at five loci, and significant departures from Hardy‐Weinberg equilibrium at two loci. Heterozygosity was not reduced in the Bush hatchery population (mean 4.3%) compared to the wild populations sampled (range, 2.9‐5.4%; mean, 4.2%). These results are discussed in relation to management of wild populations and maintenance of hatchery stocks.