Effects of increasing concentrations of fine suspended sediment on the survival, growth, condition factor and gill condition of artificially reared juveniles of Oncorhynchus masou , Salvelinus leucomaenis and Plecoglossus altivelis

Abstract

Little is known about the effect of chronic turbidity created by fine suspended sediment on the health and growth of artificially reared Oncorhynchus masou, Salvelinus leucomaenis and Plecoglossus altivelis—three important aquaculture species in Japan. This study compared survival rate, daily growth rate, condition factor (estimated from the ratio of standard length to weight) and gill condition among like‐sized juveniles exposed to fine suspended sediment (<2‐µm fraction) at concentrations of 0, 50, 100 and 500 mg/L, after 21 days. Even at 500 mg/L, there was almost no damage to the gill condition in all species. In O. masou, the daily growth rate was unexpectedly high in the 500‐mg/L treatment group, and condition factor was higher at sediment concentrations of 100 and 500 mg/L than at 0 mg/L. In S. leucomaenis, daily growth rate was significantly lower in the 500‐mg/L treatment group as compared with all other groups, but condition factor did not significantly differ among the treatments. The survival rates of O. masou and S. leucomaenis did not significantly differ among the treatment groups. In P. altivelis, neither survival rate, daily growth rate nor condition factor significantly differed among the treatments. The concentration of fine suspended sediment that affects the growth and condition factor of each of these species is likely related to their natural habitat.