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This study deals with the toxic effects of Zn2+, Cu2+, Cd2+ and NH3 on Chinese prawn (Penaeus orientalis). The median lethal concentrations of the toxic matters on Chinese prawn were determined. Cd2+>Cu2+>Zn2+>NH3-Nm is the toxic order of these chemicals to Chinese prawn. The toxic order of concentrated Zn2+ and Cd2+ in tissues and organs of Chinese prawn is in the order. gill>shell+appendage>viscera>muscle.

The toxic effects of Zn2+ on Silver Carp (Hypophthalmichthyps molitrix C. et V.), Big Head Carp (Aristrichthys nobilis Richardson), Grass Carp (Ctenopharyngodon ilellus C. et V.), and Blunt Snout Bream (Megalobrama aimbly-cephala Yih) are studied. The test results are: (1) There are linear correlations between 24h LC50 and 48h LC50 of Zn2+ for Silver Carp fingerling and temperature. 24h LC50, 48h LC50 and 96h LC50 of Zn2+ for fry of the four species are also determined; (2) There are logarithmic correlations between the growth rates of the fry and the concentrations of Zn2+ and between expansion of fish egg membranes after absorbing water and concentrations of Zn2+; (3) The tolerance of fry of the four species to Zn2+ is in the following order: Grass Carp>Silver Carp>Blunt Snout Bream>Big Head Carp; (4) The safe concentrations of Zn2+ are: Big Head Carp: 0.008 mg/L, Grass Carp: 0.046 mg/L, Blunt Snout Bream: 0.010 mg/L, Silver Carp: 0.012 mg/L, Silver Carp fingerling: 0.09 mg/L.