Cumulative Effects of Multiple Contaminants on Caged Fish

Pearl dace (Semotilus margarita) were held in cages and exposed to mine effluents, municipal wastewater effluents, a combination of the two, or to the combination in addition to runoff from a garbage disposal facility. Fish exposed to mining effluents only had the lowest mean lengths and weights but highest concentrations of As, Ni and Hg and lowest Zn in their viscera. Fish exposed to municipal wastewater effluents only had the highest concentrations of Cd and metallothionein in their viscera. Histopathological analyses of gill and liver tissues revealed a higher incidence of lesions in fish exposed to municipal wastewater effluents. These fish also had the highest LSIs, condition factors and mean vitellogenin concentrations in plasma from males. Fish exposed near the garbage disposal site had the highest concentrations of Pb and Se in their viscera.