Genetic evaluation of reintroduced amago salmon Oncorhynchus masou ishikawae

Abstract

Population revival of amago salmon Oncorhynchus masou ishikawae was attempted by reintroducing wild individuals to an isolated tributary, in which this species had once become extinct, from a neighboring tributary in the same drainage basin, and its effects were evaluated by genetic analyses with nine microsatellite markers. The number of transplants steadily increased, approximately reaching a plateau of population size two years after reintroduction. Although the revived population kept almost the same level of heterozygosity and relatedness as its founding population, the richness of alleles, especially rare alleles, has declined slightly. These results show that, in stream-dwelling fish such as amago salmon, exchange of individuals among neighboring populations in the same drainage basin is important for the long-term preservation of genetic characteristics including genetic diversity, although population revival within a short period is possible by transplanting a small number of parental fish.