Decontamination of winter flounder (Pleuronectes americanus) following chronic exposure to effluent from a pulp and paper mill

A study was conducted to determine the influence of decontamination on winter flounder living downstream from a pulp and paper mill. The fish and controls were held 8-26 weeks under contaminant-free conditions in aquaria supplied with ambient sea water. Groups of flounder, for comparison, were also sampled near the paper mill at the time of or following autopsy. No differences were apparent in length/organ-weight relationships between depurated and control groups after 26 weeks at 0-6 degrees C, but condition factor, gonadal and hepatosomatic indices, coincident with elevated levels of detoxifying enzymes, differed from field-derived samples. Pathological changes, including hemosiderin deposits in the liver and spleen, decreased, whereas pericholangitis and clear cell foci were apparent in the depurated fish and in the field samples. In two additional groups decontaminated for 8-16 weeks at 6-16 degrees C, there was no evidence of pericholangitis, but hemosiderin deposits persisted and an increase of fibrosis and clear cell foci occurred in contrast to the field group. These results suggest that some tissue repair in the liver transpired primarily during summer while other lesions, such as preneoplastic clear cell foci, which were probably induced prior to depuration, increased, but hemosiderin concentration remained unchanged. The latter observation is consistent with previous studies that suggest that hemosiderin concentration is not seasonally but age influenced.