Masculinization of Spawning Channel Catfish in the Red River of the North

Channel catfish collected from the Red River of the North included spawning female fish which exhibited secondary sex characteristics normally attributed to male catfish. Similar cases of arrenoidy have been reported in other fishes that have been linked to paper mill effluent. Aquaculture studies indicate channel catfish are sensitive to hormonal manipulations. The masculinization may represent natural variation or may be the result of endocrine disrupters, perhaps from microbially degraded plant sterols from sugar beet processing or sewage effluent.