Interaction of total dissolved gas supersaturation and suspended sediment on swimming performance of bighead carp (Hypopthalmichthys nobilis).

When dams discharge floodwaters, the river downstream often becomes supersaturated in total dissolved gases (TDG) and contains high volumes of suspended sediments (SS). Supersaturated TDG and high SS concentrations in water may affect fish physiologically in ways that manifest in swimming performance. Despite increasing awareness of the separate effects of TDG supersaturation and SS, knowledge about their synergistic effects remains unknown. To explore the interactive effects of TDG and SS on the swimming performance of bighead carp, the juveniles were exposed to 100, 110, 115, 120, 125, 130, 135, and 140% of TDG-supersaturated water with SS concentrations of 0, 50, 100, and 150 mg/L, respectively, and the critical swimming ability speed (U ) and burst swimming ability speed (U ) were measured. The results indicated that the swimming ability (U and U ) decreased when TDG levels and SS concentrations increased. TDG and SS did not interact significantly to decrease both U and U . In contrast, exposure to TDG alone significantly decreased both U and U , whereas exposure to SS alone decreased only U . In addition, our results suggested that there was a negative linear relationship between TDG and fatigue time. Swimming ability can decline significantly due to high TDG levels (>130%). Therefore, high TDG levels (>130%) should be restricted during reservoir operation to prevent the stress caused by TDG.