Relationship Between Average Heterozygosity and River Population Size in Chum Salmon

Average heterozygosity and effective size of individual river populations of chum salmon were estimated by the proportion of heterozygous enzyme loci per individual and from the number of males and females used for artificial fertilization, respectively. The heterozygosity in river populations showed a broad distribution in the range from 0.060 to 0.128, the average being 0.097. The effective river population size also showed a broad distribution in the range from 120 to 38601, the average being 6675. The estimated effective river population size was always smaller than the census number in individual river populations. The value estimated as 35.2% of its census number as the average. A significant positive correlation between the average heterozygosity and the effective size of river population was observed. We conclude that the heterozygosity of river population is difined by the effective river population size and the degree of transplantation.