Allozymic variation among populations of noble crayfish, Astacus astacus L., in southern Norway: implications for management

Abstract. The noble crayfish, Astacus astacus L., is extensively used for stocking and restocking purposes both in Scandinavia and in other European countries. It also has potential as a farmed species. Thus, it is important to have information about the genetic structuring of the species. Attempts have been made to detect genetic variability in A. astacus and find markers suitable for interpopulation discrimination. Two loci, coding for the enzymes leucine-aminopeptidase (LAP) and xanthine dehydrogenase (XDH), have previously been found to exhibit allele frequency differences among four recently established populations of crayfish in southern Norway. Eight more populations have now been studied for these and 13 other enzyme-coding loci. All of the 13 additional loci examined were found to be monomorphic. The variable zymogram bands of LAP and XDH are thought to reflect genetic variation at their encoding loci. It is suggested that the significant inter-stock allele frequency differences at these loci are to a large extent due to founder events and random genetic drift. Since information about the size and genetic characteristics of the founder populations is limited, the relative contribution of selective constraints to stock diversity cannot be assessed. For restocking strategies one should consider using both reserve populations of the original populations and other strong populations with known genetic characteristics.