Determination of the dietary absorption efficiency of hexachlorobenzene with the channel catfish (Ictalurus punctatus)

This study was designed to experimentally measure the assimilation efficiency of hexachlorobenzene (HCB) in a warm-water, benthic-feeding fish species, the channel catfish (Ictalurus punctatus). Catfish were exposed to 14C-radiolabeled HCB in catfish food over a 28-day exposure period, followed by a 14-day clearance period. Over the experimental period, the total 14C residues were measured in fish tissue and a simple two-box kinetic model was applied to the data to simulate uptake and clearance dynamics. No detectable metabolism of HCB by catfish was found. A two-box kinetic model effectively modeled the uptake and clearance of 14C-HCB in catfish, with a calculated assimilation efficiency of the chemical into the whole catfish of 67% (growth corrected). The growth-corrected pseudo first-order elimination half-life of 14C-HCB from whole catfish was determined to be 29 days (k2=0.024 day−1).