Influence of total dissolved gas-supersaturated water on silver carp (Hypophthalmichthys molitrix)

Abstract

Dam discharges over spillways are the main reason for the gas-supersaturated water generated in rivers. Local aquatic organisms, especially fish, readily develop gas bubble disease (GBD) in a river with total dissolved gas supersaturation (TDGS). Sometimes, fish will die after a specific exposure period, which negatively affects the biological equilibrium. In this study, the influence of TDGS on silver carp was explored. Silver carp were exposed to gas-supersaturated water with TDGS levels of 140%, 135%, 130%, 125%, 120%, and 110% to test the impact of TDGS. Some silver carp died when the TDGS level was 120% or higher, and all the silver carp exposed to a TDGS level of 140% died within 10 h. In comparison with the Chinese sucker, Prenant's schizothoracin, and rock carp, silver carp seem less sensitive to TDGS. In addition, we tested the catalase (CAT) activity in the muscles and gills of silver carp after they were exposed to gas-supersaturated water with a TDGS level of 140%. The CAT activity changed with time; it increased first and then decreased until it was lower than the initial CAT activity. The results of this study can provide basic data for developing a standard for environmental evaluation.