Genetic variation within and among Danish brown trout ( Salmo trutta L) hatchery strains, assessed by PCR-RFLP analysis of mitochondrial DNA segments

Eleven Danish brown trout hatchery strains were studied by PCR- RFLP analysis of the ND-I and ND-5/6 segments of the mitochondrial genome. For comparison, data from wild trout representing three Danish river systems also were included. Reduced variability in terms of nucleon diversity and number of haplotypes was observed in most hatchery strains. However, computer simulations showed that even with relatively large numbers of female spawners considerable loss of haplotypes could take place over time. Therefore, reduced variability in some of the strains did not necessarily indicate a critical loss of allelic Variation at nuclear loci. The genetic relationships among the strains were compared with information from hatchery managers on the origin of the strains. In one case, a strain supposed to be recently founded from wild trout appeared to be of a mixed wild and hatchery origin. Genetic differentiation among strains (Phi(ST) = 0.23) was of the same order of magnitude as that observed among wild Danish trout populations. However, minimal differentiation (Phi(ST) = 0.01) was observed among the four quantitatively most important strains, supplying 80% of all hatchery trout stocked in Denmark. (C) 1997 Elsevier Science B.V.