Abstract
To clarify the distribution and genetic characteristics of the Ayu Plecoglossus altivelis altivelis on islands in the Tsushima Current area, ecological and genetic investigation was made at eight islands in four major islands or islandgroups, i.e. Cheju Island, Gotou Islands, Tsushima Islands and Oki Islands. We found the Ayu at seven islands in all the four island-groups. Genetic examination with allozyme electrophoresis revealed considerable allele frequency differences between populations of Dougo Island and the other areas at the PGM-1 locus (p<0.001) and also between those of Fukue Island and the others at the GPI-1 locus (p< 0.001). Although size of these two populations on relatively small islands seemed to be small, genetic variability within each population did not appear so small. These suggest that genetic differentiation of these populations has been primarily due to random genetic drift on smaller islands but has accumulated during a considerable length of time, say several thousand years. We discussed importance of protection of their habitats to conserve these genetically unique populations of the Ayu on small islands.
