Microsatellite analysis of hatchery stocks and natural populations of Arctic charr, Salvelinas alpinus, from the Nordic region: implications for conservation

Semi-automated fluorescent genotyping of eight polymorphic microsatellite l oci was used to assess the level of genetic diversity and population differ entiation in Nordic stocks of non-anadromous Arctic charr, Salvelinus alpin us, of both wild and hatchery origin. Highly significant genetic heterogene ity was detected globally across wild and/or hatchery populations and even between populations from lakes separated by as little as six kilometres. Th e overall level of genetic differentiation among wild populations (F-ST = 0 .360) was substantially higher than that observed between populations of an adromous Arctic charr in Canada using microsatellite data. Cavalli-Sforza a nd Edward's chord distance was used to construct a neighbour-joining tree a nd three population clusters were supported with relatively high bootstrap values which included the populations from north-west, north-east and south ern Finland respectively. Use of Paetkau et al's individual assignment rest further supported the strong differentiation of most populations as well a s their classification into the three predicted geographical areas. No sign ificant difference in average allele number or heterozygosity was observed between populations of wild and hatchery origin. However, the effects of ha tchery rearing were revealed by a strong increase in the number of deviatio ns from Hardy-Weinberg equilibrium as well as of linkage disequilibrium eve nts in the hatchery stocks compared to natural populations. The population from Lake Saimaa; in south-cast Finland, is completely reliant upon aquacul ture assistance for its survival. The broodstocks of this population exhibi ted particularly low levels of genetic variability. Although the hatchery s tocks of this population suffer from increased egg and alevin mortality and disease susceptibility, it remains to be determined if this is due directl y to a lack of genetic variation as some abundant unstocked natural populat ions possessed similarly low levels of microsatellite variability.