The effect of malathion, diazinon, and various concentrations of zinc, copper, nickel, lead, iron, and mercury on fish.

Acute and chronic toxicity tests for malathion, diazinon, copper (Cu), mercury (Hg), lead (Pb), zinc (Zn), nickel (Ni), and iron (Fe) were conducted. Mortalities of Barilius vagra and Cyprinus carpio (common carp) were variable but LC50-96 hr were similar for pesticides. Adult B. vagra seem to be more sensitive to malathion than juvenile carp. Both juvenile carp and adult B. vagra were extremely sensitive to diazinon. Long-term exposure to pesticides modified morphology and behavior. The LC50-96 values for Cu, Hg, and Pb were 0.3, 0.16, and 0.44, respectively, for smaller fish and 1.0, 0.77, and 1.33, respectively, for larger fish. Replicate LC50 values for Zn, Ni, and Fe were somewhat variable, and for these metals, the size of the fish seemed to affect response because LC50 values increased as fish size increased. Copper, Pb, Zn, and Fe residues following exposure to sublethal concentrations of these metals for 15 d were significantly greater in whole juvenile common carp than in controls.