Abstract
The existing Formosan landlocked Masu Salmon (Oncorhynchus masou formaosanus) has distributed only in a protected eight-kilometer section of the Chi-Chia-Wan River located in the Sheh-Bah National Park. Although the Masu Salmon in this area has been well protected, its population size has not distincitively enlarged. Therefore, it is a significant object to increase the population of the Masu Salmon. This report has revealed the investigation of the Masu Salmon during the past decade and analyzed the monitoring results of the surroundings. It has also described the fluctuation status of the Masu Salmon's population size in this area and discussed the possible influence factors and the methods of the conservation. Since 1994, the population and distribution of the Masu Salmon in the Chichiawan Stream has systematically investigated. It has revealed that not only the population of the Masu Salmon has violently fluctuated; its distribution status has also been distinctively changed. The minimum of its total amount of population was only 554 (in 1995 summer), however, the maximum 2,495 (in 1995 winter). Their difference is over four times. From the analysis of its fluctuations, it can be found that the weather status of the breeding seasons, from early October till late November, plays a significant factor. The floods of typhoon will destroy the breeding habitats. This weather factor is strongly relative to the population size of the Masu Salmon. Salmon breeding habitats destroyed by Typhoon will affect the recruitment of the population. Before being able to solve the problems of the partition of salmon population caused by the dam, it is suggested that artificial breeding be adopted in order to move larva salmon to suitable upstream habitat to keep from the extinction of the upstream salmon population. This method might be the efficient strategy at this monment.