Swimming and Recovery Abilities of Juvenile Chinese Sturgeon Acipenser sinensis

Breeding populations of the Chinese Sturgeon Acipenser sinensis are endemic to the Yangtze River in China, but other wild populations have been extirpated, and the species is critically endangered. The swimming performance of juvenile Chinese Sturgeon was tested in a flume-type respirometer using a three-phase test: a constant velocity endurance test, followed by a 30-min recovery period, and then a stepped velocity test to determine the critical swimming speed (U-crit). Swimming endurance (at 19 +/- 1 degrees C) was tested at five constant speeds: 3.0, 3.5, 4.0, 4.5, and 5.0 body lengths per second (BL/s) (groups 1-5). A control group (group 0) was used to determine U-crit for fish that had not been subjected to the endurance test. The U-crit of the control group (U') was 4.32 +/- 0.30 BL/s (mean +/- SE) and after fish had completed the endurance test the U-crit ranged from 2.88 +/- 0.15 BL/s in group 1 to 3.64 +/- 0.28 BL/s in group 5, with corresponding recovery ratios (U-crit/U') of 66.7 +/- 3.4% and 84.3 +/- 6.4%. Endurance time decreases with swimming speed, so these results indicate that fatigue resulting from swimming at low speed for a longer time requires more recovery time than does fatigue resulting from swimming at high speed for a shorter time. The relationship between swimming speed (U; BL/s) and endurance time (t(e); min) is described by logt(e) = 3.90 - 0.64U (r(2) = 0.769, P < 0.05).