Fingerling channel catfish (Ictalurus punctatus) were given diets containing 0, 0.4, 0.8, or 4.0 I?g dieldrin/g of food (dry weight) for 210 days, followed by a dieldrin-free diet for 56 days. Catfish receiving 4.0 I?g dieldrin/g food gained about 17% less weight than the control fish in 210 days and about 35% less weight during the last 126 days of the 210-day period. No growth differences were attributable to the ingestion of 0.4 or 0.8 I?g dieldrin/g of feed. Mortality during the experiment was random and not appreciable. Dieldrin accumulations were characterized by an immediate rapid rise of residue levels in the tissues, followed by a period during which concentrations were relatively stable. Residues in tissues decreased rapidly after dieldrin was withdrawn from the diet. Dieldrin half-life was 9.6 days (mean for the three groups). Theoretical residue concentrations calculated from the growth, feeding, and half-life data were similar to the empirical concentrations, although the theoretical values were consistently the higher. The recoverable concentration accounted for 25.7% (mean of the three treatments) of the theoretical concentration.
