Abstract: To investigate the effects of water-borne lead (Pb) on the swimming capability and metabolism of jevenile grass carp (Ctenopharyngodon idella), critical swimming speed (U_crit) and oxygen consumption rate (MO₂) were measured in water with four concentrations of Pb²⁺ (0, 0.75, 2.24, 3.73 mg·L^-1) at 20 ℃. The results showed that after exposure to 3.73 mg·L^-1 Pb²⁺, U_crit significantly decreased (P<0.05), being 91.22% of that of the control group. The swimming speed was linearly correlated withMO₂. With the increase of Pb²⁺ concentration, the difference of the maximum and minimum oxygen consumption rate increased first and then decreased. It was decreased by 17.68% after exposure to 3.73 mg·L^-1 Pb²⁺ compared to the control group. Exposure to low concentration of Pb²⁺ decreased the oxygen consumption efficiency, which might be the main reason for the decrease of the swimming capability of grass carp. Ourresults could be used to assess and control water Pb²⁺ risk in river and thus provide reference for environmental management.

Key words: particulate matter, water-insoluable particles, water-soluble particles, diameter distribution.