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 LC₅₀ of Hg²⁺ 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 Cu²⁺0.17 mg L⁻¹, 0.09 mg L⁻¹, and 0.12 mg L⁻¹ respectively; of Cd²⁺6.5 mg L⁻¹, 18.47 mg L⁻¹, 5.36 mg L⁻¹, respectively; and of Zn²⁺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 Hg²⁺ and Cu²⁺ (P<0.05), and the Vf and Va of the 3 species rose initially and then declined when exposed to Cd²⁺. Zn²⁺ 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 Hg²⁺, Cu²⁺, Cd²⁺, and Zn²⁺, 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.