Integrated habitat monitoring of environmental features to site the releasing of cultivated Oncorhynchus masou formosanus

Abstract

Abstract The Formosan landlocked salmon (Oncorhynchus masou formosanus), an endangered species, had ever inhabited in the upper branches of stream Da-Chia of Taiwan in 1940s. However, the distribution of the salmon gradually declined and was only observed in stream Chi-Chia-Wan and stream Kao-Shan in last decades. Shei-Pa National Park has ever devoted to restoring the salmon and releasing the cultivated breeds into several historic rivers. Therefore, a comprehensive and systematic monitoring and assessment of the habitat candidates is indispensable to gain the successful propagation of released salmon. This study presents a methodology for determining the optimal juveniles’ releasing sites in association with the water quality and channel’s physical features. Five historic inhabiting streams with nine monitoring sites for cultivated breeds release were selected. Three reference sites were chosen as various levels, i.e. the best, the mild interfered, and the worst circumstance for the salmon, to evaluate the candidate sites. The three reference sites located in the stream where the Formosan salmon could naturally propagate. The results indicated that the overall habitat quality of stream Lo-Ye-Wei (potential releasing site Y#1) was superior to the other sites. The increase of fish population in the Lo-Ye-Wei was significant with a total of 1269 fish in 2012 over 2.5 times the amount of 519 fish in 2011. This significant boost of salmon population in Lo-Ye-Wei indicated that the siting strategy proposed in this study is feasible for the salmon release.