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 wint er flounder living downstream from a pulp and paper mill. The fish and cont rols were held 8-26 weeks under contaminant-free: conditions in aquaria Sup plied with ambient sea water. Groups of flounder, for comparison, were also sampled near the paper mill at the time of or following autopsy. No differ ences were apparent in length/organ-weight relationships between depurated and control groups after 26 weeks at 0-6 degrees C, but condition factor, g onadal and hepatosomatic indices, coincident with elevated levels of detoxi fying enzymes, differed from field-derived samples. Pathological changes, i ncluding hemosiderin deposits in the liver and spleen, decreased, whereas p ericholangitis and clear cell foci were apparent in the depurated fish and in the field samples. In two additional groups decontaminated for 8-16 week s at 6-16 degrees C, there was no evidence of pericholangitis, but hemoside rin deposits persisted and an increase of fibrosis and clear cell foci occu rred 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 th at hemosiderin concentration is not seasonally but age influenced.