EFFECTS OF AZINPHOS-METHYL ON THE REPRODUCTIVE SUCCESS OF THE BLUEGILL SUNFISH, LEPOMIS-MACROCHIRUS, IN LITTORAL ENCLOSURES

Adult bluegills were exposed to a single application of azinphosmethyl in 12 littoral enclosures in a northern Minnesota pond, Responses mea sured were adult behavior and spawning, embryo hatchability, larval su rvival until swim-up, young-of-year (Y-O-Y) growth, and total biomass, Four enclosures each were treated at 1.0 and 4.0 mu g/liter and four remained untreated, The half-life of azinphos-methyl was 2.3 and 2.4 d ays at each of the two treatment levels, respectively, Quantifiable re sidues remained in the water for 8 days, Concentrations of 4.0 or 1.0 mu g/liter did not cause any significant long-term (63 day) effects on bluegill reproduction, embryo hatchability, Larval survival, growth, or biomass, Although important bluegill prey such as copepod nauplii a nd cladocerans were significantly or greatly reduced by Day 7 followin g treatment, they recovered to levels equal to or greater than some of the control enclosures by Day 35. The apparent lack of significant lo ng-term effects on reproductive success can be partially explained by the relatively short half-life of azinphos-methyl in littoral enclosur es. (C) 1995 Academic Press, lnc.