Acute Toxic Effect Of Water-borne Lead On Six Fishes From The Upper Reaches Of The Yangtze River

In order to estimate the tolerances of 6 fishes from the Yangtze River to the toxicity of water-borne lead(Pb), median lethal concentration of Pb for 96 hours(96 h LC50) in Grass Carp(Ctenopharyngodon idellus), Crucian carp(Carassius auratus), Southern Catfish(Silurus meridionalis), Bluntnose black bream(Megalobrama amblycephala),Chinese Sucker(Myxocyprinus asiaticus) and Spinibarbus sinensis(Spinibarbus sinensis) were tested at same water temperature(27.5 ± 0.2 ℃), hardness(10 ± 0.5mg/L Ca CO3) and pH(7.0 ± 0.1).The main results from this study as follows:1. In the acute exposure experiments, the mortalities of of Grass Carp, Crucian carp,Southern Catfish, Bluntnose black bream, Chinese Sucker and Spinibarbus sinensis increased with increasing lead concentrations. Using the method of a straight line interpolation, the values for 96 h LC50 in the 6 fishes were 3.73, 11.59, 6.59, 3.27, 0.33 and 3.00 mg Pb/L, respectively.2. In each species the lead accumulation of the tested fish body increased with increasing Pb concentration.3. Statistical analysis showed that the lead accumulation in the dead fish was not influenced by its death time for the same species. The mean value of lead content of the dead fish in each species was higher than that of the survivors, and except for S.meridionalis the differences were significant(p < 0.05) between the dead and the survivor in the other 5 species.The conclusions were as follows:1. The results suggested that the tolerances for Pb toxicity were different among the sixspecies and the order was C. auratu>S. meridionalis>C. idellus>M. amblycephala>S. sinensis>M. Asiaticus.2. Compared to other five fish species in this study, the 96 h LC50 with water-borne lead exposure in C. auratus was higher. Due to the strong resistance capacity of hypoxia and high Pb excretion ability, Carassius auratus was more tolerant to lead toxicity.3. Compared to other 5 fish species in this study, the 96 h LC50 with water-borne lead exposure in M. Asiaticus was lower, which indicated M. Asiaticus have low tolerance for lead toxicity. The water-borne lead might be the main cause of the endangered M.Asiaticus.4. Pb was less toxic in harder water to fish and larger fish was more tolerant to Pb toxicity. The lead accumulation in the dead fish was not influenced by its death time for the same species.5. the accumulation in the dead fish was higher than that in the survivor when exposed to a same Pb concentration.