Population genetic structure of lobster (Homarus gammarus) in Norway, and implications for enhancement and sea-ranching operation

Lobster stock enhancement in Norway is based on selection of wild broodstoc k and artificial production of juveniles which are released into the natura l environment. Four enzymes (malic enzyme, phosphoglucomutase (two loci), i socitrate dehydrogenase and glucosephosphate isomerase) were used to screen genetic variation in 22 different populations (about 2580 individuals) alo ng the coast. Minor but statistically significant variation in allele frequ encies was found for all five loci. The sample collected from the most nort hern and isolated population, in Tysfjord, was polymorphic for only a singl e locus and contributed substantially to the overall sample heterogeneity. Except in some pairwise tests, no significant variation was found when test ing the samples within the Skagerak and Vestland regions. The samples colle cted in the More-Trondelag region show significant variation for one locus (PGM-2*), which were confirmed in pairwise tests for genetic differentiatio n. Future activities aiming on local stock enhancement should evaluate the risk for unwanted genetic impacts. Commercial ranching operations of lobste r, including selective breeding, should be carried out only in areas with l ow levels of genetic differentiation. (C) 1999 Elsevier Science B.V, All ri ghts reserved.