Site fidelity of and habitat use by the Formosan landlocked salmon (Oncorhynchus masou formosanus) during typhoon season in Chichiawan Stream, Taiwan as assessed by nano-tag radio telemetry. Zoological Studies 48(4): 460-467. Movements of (time-series horizontal position) and habitat use by adult Formosan landlocked salmon (Oncorhynchus masou formosanus) were examined in a Taiwanese stream, (Chichiawan Stream) using nano-tag telemetry in summer (typhoon season) 2007. A great flood caused by a typhoon occurred during the tracking period in this study, but the flood did not change the positions or habitat use by the adult salmon. Ten tagged fish predominately used microhabitats near boulders and made frequent short movements of <200 m between habitats. Our results suggest that adult salmon are basically sedentary in summer, but undertake small-scale movements to secure food. In conclusion, this study provides useful information for the conservation of the Formosan landlocked salmon by showing that boulders in streams may serve as refuges from floods brought by typhoons.