GENETIC-VARIATION WITHIN AND AMONG DANISH BROWN TROUT (SALMO-TRUTTA L) HATCHERY STRAINS, ASSESSED BY PCR-RFLP ANALYSIS OF MITOCHONDRIAL-DNASEGMENTS

Eleven Danish brown trout hatchery strains were studied by PCR-RFLP an alysis of the ND-I and ND-5/6 segments of the mitochondrial genome. Fo r comparison, data from wild trout representing three Danish river sys tems also were included. Reduced variability in terms of nucleon diver sity and number of haplotypes was observed in most hatchery strains. H owever, computer simulations showed that even with relatively large nu mbers of female spawners considerable loss of haplotypes could take pl ace over time. Therefore, reduced variability in some of the strains d id not necessarily indicate a critical loss of allelic Variation at nu clear 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 differenti ation among strains (Phi(ST) = 0.23) was of the same order of magnitud e as that observed among wild Danish trout populations. However, minim al differentiation (Phi(ST) = 0.01) was observed among the four quanti tatively most important strains, supplying 80% of all hatchery trout s tocked in Denmark. (C) 1997 Elsevier Science B.V.