Effects of total dissolved gas supersaturated water at varying suspended sediment concentrations on the survival of rock carp Procypris rabaudi

Abstract

High total dissolved gas (TDG) levels and excessive suspended sediment (SS) concentrations greatly threaten the survival of fish downstream of dams when flood discharge occurs. However, few studies have investigated the impacts of TDG and SS on fish. To evaluate the effects of TDG and SS on rock carp, juveniles were exposed to 125, 130, 135 and 140% TDG supersaturated water with SS concentrations of 0, 200, 600 and 1000 mg/l, respectively, and after the exposure period, the rock carp showed noticeable abnormal behaviours and signs of gas bubble disease. The survival rate decreased with increases in the TDG levels and SS concentrations. Moreover, an increase in the SS concentration in the TDG supersaturated water resulted in a decrease in the median survival time (ST50). Combined exposure to TDG and SS exerted a significant effect on the survival of rock carp. This study indicates that TDG supersaturated water with SS might be a notable threat to rock carp survival during flood discharge.