A continuous monitoring system, consisting of an apparatus to detect light beam interruptions as a sign of aberrations in fish movement patterns, has been used to study the effects of fish exposure to lethal and sublethal concentrations of zinc. In addition to the exposure monitoring, the growth and reproductive success of exposed bluegill (Lepomis macrochirus) were studied. In the movement tests, Notemigonus crysoleucas and Carassius auratus were exposed to 2.94-3.64 mg/l zinc ions as zinc sulfate for 96 hrs. The light system detected premortal movement aberrations allowing for survival of test fish by condition reversal. Analysis of LD50 levels was accomplished and recorded by atomic absorption spectrophotometry twice daily. Growth and reproduction tests involved exposure of one male and 3 females to Zn concentrations about equal to 0.1-0.01 of the lowest concentration detected by the monitoring tests. Eggs were collected and hatched separately. Concentrations of one-tenth the lowest zinc concentrations eliminated reproduction in the bluegills.