Ecological performance of red drum (Sciaenops ocellatus) larvae exposed to environmental levels of the insecticide malathion.

Malathion is a highly soluble organophosphate insecticide that is widely used in agriculture and mosquito eradication campaigns. Fish species, such as red drum (Sciaenops ocellatus), that use seagrass beds as nursery areas could be affected by runoff waters contaminated with malathion. We exposed red drum larvae at the size they reach in estuarine nursery areas to environmentally realistic and sublethal levels of malathion (0, 1, and 10 microg/L). We evaluated the effects of such exposure on ecologically significant behaviors (routine swimming and predator evasion), growth, and resting metabolism. Malathion exposure to relatively low but ecologically realistic concentrations did not affect routine behavior, escape behavior, resting metabolic rate, or growth, indicating that reported environmental levels may be safe for young fishes. However, a recent substantial increase in the use of malathion may elevate surface-water concentrations to levels above those tested in the present study.