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Eighteen 0.4-ha earthen ponds in northwest Mississippi were used in a 3-year study to evaluate the effect of weekly copper sulfate applications on the incidence and economic impact of environment-induced off-flavors in channel catfish Ictalurus punctatus. Each spring, when water temperatures increased above 20°C, nine ponds were treated weekly with 0.12 mg Cu/L. Treatments were discontinued each fall when water temperatures fell below 20°C. Overall prevalence of off-flavor was reduced by 80% for ponds treated with copper sulfate compared with control ponds, and episodes of off-flavor were of shorter duration in treated ponds. Off-flavors never delayed fish harvest from treated ponds, whereas off-flavors delayed fish harvest on 10 occasions in control ponds. Average annual fish harvest was 5,900 kg/ha from ponds treated with copper sulfate and 5,349 kg/ha from control ponds. The 9% reduction in fish …