GENETIC DIFFERENTIATION AMONG CHUM SALMON, ONCORHYNCHUS-KETA (WALBAUM), FROM PRIMORYE AND SAKHALIN

Mitochondrial DNA (mtDNA) was examined in six wild populations of chum salmon (Oncorhynchus keta Walbaum) distributed over the Primorye Region which extends approximately 1000 km along the Sea of Japan coast, and six populations from Sakhalin, using restriction enzyme analysis. By means of two restriction enzymes (Bam HI and Eco 81I) eight mtDNA clonal lines were revealed in the 346 chum salmon studied. Mitochondrial DNA variants grouped the fish into two major clusters representing the Primorye and Sakhalin regions. Analysis of different chum salmon generations showed stability in the temporal population genetic structure in the three Primorye populations studied, but instability in the Sakhalin population of the Naiba River. We succeeded in detecting four major mtDNA clonal variants in Primorye chum salmon. The geographic distribution of clonal frequencies in Primorye populations has a clinal U‐shape associated with the north‐south axis of the Primorye region. On the whole, Sakhalin populations are less heterogeneous than Primorye ones. Two hatchery‐seeded stocks from south west Sakhalin showed no mtDNA clonal variation. Copyright © 1992, Wiley Blackwell. All rights reserved