Acute toxicity of carbaryl, methiocarb, and carbosulfan to the rainbow trout (Oncorhynchus mykiss) and guppy (Poecilia reticulata)

The acute toxicity of carbaryl, methiocarb and carbosulfan to juvenile rainbow trout (Oncorhynchus mykiss; 1.92 +/- 0.5 g) and guppies (Poecilia reticulata; 0.45 +/- 0.04 g) was evaluated in 96-h toxicity tests under static conditions. Concentrations in the toxicity test ranged from 0.85 to 8.5 mg/l for carbaryl, from 0.7 to 28.0 mg/l for methiocarb, and from 0.031 to 12.5 mg/l for carbosulfan. Carbaryl and methiocarb were more toxic to rainbow trout than to guppies. However, compared with rainbow trout, guppies were more sensitive to carbosulfan. The incidence of mortality in fish increased significantly (P < 0.05) with increasing pesticide concentrations. The time required to kill 50% (LT50) of the rainbow trout at the lowest concentrations of carbaryl, methiocarb, and carbosulfan was 51 h 12 min, 74 h 35 min, and 107 h 57 min, respectively. As insecticide concentrations were increased, LT50 values decreased (P < 0.05).