Abstract
This study aimed to estimate the artificial retarding basin as refugia for a freshwater minnow (Zacco platypus) in a river. Fish samples were collected from the Sakaigawa River channel, Izumi River channel of branch river in Sakaigawa River, and two ponds in retarding basin of the Sakaigawa Yusuichi Park before and after rain flush events in 2010 and 2011. Stable isotope ratios of carbon and nitrogen (δ13C and δ15N) were determined for the fishes. The δ13C and δ15N for the fish in the river channels (around -26‰ and 16‰, respectively) were different from those in the retarding basin (around -22‰ and 11‰) before rain flush events. The stable isotope ratios for the fish samples have shown that some fish which had lived in the river channel moved to the retarding basin during flood events.
