SWIMMING BEHAVIOR OF Tribolodon hakonensis AROUND SPUR DIKE IN NORMAL FLOW

Abstract

 In this study, the authors aimed at clarifying river environment functions of spur dike focusing on swimming behaviors of Tribolodon hakonensis in normal flow. Therefore, we carried out behavior experiments and hydraulics experiments using fish and columns with relatively large diameters. Results revealed that the presence points of fish mainly were two patterns, 1) a column group and 2) downstream site of the column group. Further, fish was mainly presented the downstream site of the columns in the case of the column group. The flow rate of the place was less than 4BL/s and the fish chose the flow that was lower than the cruising velocity, we presume. Further, difference occurred between the cases in the flow of the transverse direction in the downstream site of the columns although difference did not occur in time of fish's presence in the column group of the fish in each case. This is because the flow rate v of the downstream site of the column was less than 2BL/s and the fish were not affected by the flow rate, we infer. Further, the column installation interval in the identical y-axis was wider than the fish's length, which made it easier for the fish to present in the column group, we presume.