Tolerance and Avoidance Behavior towards Gas Supersaturation in Rock Carp Procypris rabaudi with a History of Previous Exposure

Abstract

AbstractTotal dissolved gas (TDG) supersaturation on the upper Yangtze River basin is becoming increasingly serious because of the intense construction of high dams, posing a threat to resident fish. The tolerance and behavior characteristics of Rock Carp Procypris rabaudi preexposed to TDG‐supersaturated water were evaluated by placing juveniles (weight 6.4 ± 1.67 g, fork length 7.2 ± 0.7 cm; mean ± SD) in 35‐cm‐deep tanks at 130% supersaturation for 2.33 h as preexposure. Surviving fish were allowed 5 d of recovery in saturated‐equilibrium (100% TDG) water and then examined in an acute lethality experiment at TDG supersaturation values of 120, 125, 130, 135, 140, and 145%. The resulting median lethal times were 10.4, 4.6, 3.2, 2.1, 1.4, and 1.4 h, respectively. The preexposed fish showed a poorer tolerance to TDG‐supersaturated water than did a control group that were not preexposed for TDG above 120% supersaturation (P < 0.05 in cases where there was a significant difference between individual groups). Experiments on horizontal behavior and vertical behavior used the same preexposure routine, followed by 5 d of recovery in saturated‐equilibrium water. For all behavior experiments, both the preexposed and control groups showed significant avoidance responses to TDG‐supersaturated water; however, there were no significant differences between the preexposed and control groups.