ABSTRACT

Fishes are subjected to long-term stress arising from exposure to sublethal concentrations. These sublethal concentrations may prove more deleterious than the lethal concentrations, because subtle and small effects on the fish may alter their behavior, feeding habits, position in the school, reproductive success, etc. This chapter discusses such effects of pesticides on fish. Of all the pesticide-induced biochemical changes, inhibition of acetylcholinesterase (AChE), the enzyme involved in terminating the action of the neurotransmitter acetylcholine, is perhaps the most often studied. Many morphological changes have been reported following the exposure of fish either to high concentrations for brief periods, or to sublethal concentrations for extended periods. Cumulative mortality of such exposed fry was nearly twice that of the control fry, although there was no significant difference in the growth, swimming performance, predator avoidance, temperature avoidance, and metabolism of the fry. Fathead minnows, channel catfish, and bluegills exposed to phosphate esters became hypersensitive to disturbance, fed less, and showed impaired swimming ability.