Rheotaxis and swimming performance of Perch-barbel (Percocypris pingi, Tchang, 1930) and application to design of fishway entrances

The objective of this research was to determine the effects of diel cycle and flow velocity on rheotaxis, measure the swimming performance of Perch-barbel (Percocypris pingi, Tchang, 1930) and use the results to recommend an appropriate fishway entrance velocity and fish lift operating schedule. PIT tagging was used to monitor fish rheotaxis for 48 h in four channels with differing flow characteristics. Swimming performance tests were conducted in a swimming respirometer and induced flow speed, critical swimming speed and critical burst speed were determined. The relationship between flow velocity and fish swimming behavior was analyzed to determine the optimal attraction flow velocity. There were three primary findings. (1) Test fish were active both day and night, but made more attempts, had longer retention times, and swam longer through-water distances in all channels during the day. (2) Entry, retention, and effort were maximum at a flow velocity of 0.2 m/s (26% of absolute critical swimming speed (m/s) and 29% of relative critical swimming speed (bl/s)). (3) Attempt number, retention time and through-water distance increased with body length in the channel with greatest activity. Collectively, these data suggest that passage of P. pingi will be optimized by fishways operating throughout the day and most of the night, although these conditions could lead to size-based selectivity in passage