Acute Toxicity, Respiratory Reaction, and Sensitivity of Three Cyprinid Fish Species Caused by Exposure to Four Heavy Metals

Using 3 cyprinid fish species zebra fish, rare minnow, and juvenile grass carp, we conducted assays of lethal reaction and ventilatory response to analyze sensitivity of the fish to 4 heavy metals. Our results showed that the 96 h LC 50 of Hg 2+ to zebra fish, juvenile grass carp, and rare minnow were 0.14 mg L −1 , 0.23 mg L −1 , and 0.10 mg L −1 , respectively; of Cu 2+ 0.17 mg L −1 , 0.09 mg L −1 , and 0.12 mg L −1 respectively; of Cd 2+ 6.5 mg L −1 , 18.47 mg L −1 , 5.36 mg L −1 , respectively; and of Zn 2+ 44.48 mg L −1 , 31.37 mg L −1 , and 12.74 mg L −1 , respectively. Under a 1-h exposure, the ventilatory response to the different heavy metals varied. Ventilatory frequency (Vf) and amplitude (Va) increased in zebra fish, juvenile grass carp, and rare minnows exposed to Hg 2+ and Cu 2+ (P<0.05), and the Vf and Va of the 3 species rose initially and then declined when exposed to Cd 2+ . Zn 2+ had markedly different toxic effects than the other heavy metals, whose Vf and Va gradually decreased with increasing exposure concentration (P<0.05). The rare minnow was the most highly susceptible of the 3 fish species to the heavy metals, with threshold effect concentrations (TEC) of 0.019 mg L −1 , 0.046 mg L −1 , 2.142 mg L −1 , and 0.633 mg L −1 for Hg 2+ , Cu 2+ , Cd 2+ , and Zn 2+ , respectively. Therefore, it is feasible to use ventilatory parameters as a biomarker for evaluating the pollution toxicity of metals and to recognize early warning signs by using rare minnows as a sensor.