 largemouth bass ( lmb ) , micropterus salmoides , were taken from the escambia river ( contaminated site ) and the blackwater river ( reference site ) near pensacola , florida . 
 the escambia river collection occurred downstream of the effluent from two identified point sources of pollution . 
 these point sources included a coal - fired electric power plant and a chemical company . 
 conversely , the blackwater river 's headwaters and most of its length flow within a state park . 
 although there is some development on the lower part of the blackwater river , fish were collected in the more pristine upper regions . 
 fish were captured by electroshocking and were maintained in aerated coolers . 
 physical measurements were obtained , blood was taken , and liver and gonads were removed . 
 lmb plasma was assayed for the concentration of 17ss - estradiol ( e2 ) and testosterone using validated radioimmunoassays . 
 the presence of vitellogenin was determined by gel electrophoresis ( sds - page ) and western blotting using a monoclonal antibody validated for largemouth bass vitellogenin . 
 no differences in plasma concentrations of e2 or testosterone were observed in females from the two sites . 
 similarly , males exhibited no difference in plasma e2 . 
 however , plasma testosterone was lower in the males from the contaminated site , as compared to the reference site . 
 vitellogenic males occurred only at the contaminated site . 
 additionally , liver mass was proportionately higher in males from the contaminated site , as compared to males from the reference site . 
 these data suggest that reproductive steroid levels may have been altered by increased hepatic enzyme activity , and the presence of vitellogenic males indicates that an exogenous source of estrogen was present in the escambia river.imagesfigure 1figure 2figure 3figure 4figure 5figure 6 
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