Abstract
The genetic diversity of the endangered species Oncorhychus masou formosanus,has attracted increasing attention. This study applied isozyme electrophoresis and mitochondria DNA sequencing to analyze the genetic diversity within and among populations in Taiwan and Japan. As the isozyme experiment results indicated, only one out of twenty three loci expressed minor genetic variations. It implies low genetic diversity(Ho=0), and the F-statistic analysis demonstrated the populations in Taiwan tended to inbreed. The DNA sequencing data lead to three main conclusions: One, the genetic distances between anadramous and landlocked populations in Japan is far greaterthan the distances within population, which indicated that anadramous and landlocked populations are gradually diverging. Two, landlocked populations in Taiwan and Japan differ genetically slightly. This situation is common among Pacific salmon genera. However, the diversity of the Japan population (four genotypes in seven specimen) is greater than that Taiwan''s (two genotypes in twelve specimen). Three, the Taiwan population exhibits low genetic diversity. The base pair difference between the two genotypes dedicates a genetic distance of 0.0001. As a result, one of the essential efforts to preserve this precious species lies on maintaining and increasing the genetic diversity of the population.