Movement patterns of three freshwater fish species after upstream transportation by fishway in the Jangheung Dam

We investigated the post-passage movement patterns of three freshwater fish species, Carassius auratus, Hemibarbus longirostris, and Silurus asotus, frequently captured in a fishway trap as they were released into the lentic dam reservoir. Acoustic telemetry was used to monitor fish movement. Acoustic tags were attached to 10 individuals (C. auratus, [n = 6], Ca1–6; H. longirostris, [n = 2], Hl1 and Hl2; and S. asotus, [n = 2], Sa1 and Sa2). The individual (Sa1) was particularly monitored to changes of vertical distribution between day and night a depth transmitter. The lentic species, C. auratus and S. asotus, were grouped into those that moved into upper streams (Ca1, Ca2, Ca3, and Sa1) and those that stayed in the reservoir (Ca4, Ca5, Ca6, and Sa2); all individuals utilized almost the entire area of the reservoir. However, H. longirostris, which favor lotic environments, showed different responses; one (Hl1) immediately moved into one of upper the streams, whereas the other (Hl2) utilized the entire dam reservoir area. No significant correlations were observed between size of the C. auratus individuals (total length and total weight) and monitored parameters (total movement distance, movement distance per day, and number of receivers encountered). Moreover, S. asotus used the water at a mean depth of 2.89 ± 1.52 m, and its vertical distribution changed more actively during the night than that during the day. Therefore, the efficacy of the Jangheung Dam fishway could be improved through release of the confluence of the inflow streams at the dam reservoir, which would provide both lentic and lotic environments without extended migration for fish.