Wiener, J. G., 1983, Comparative analyses of fish populations in naturally acidic and circumneutral lakes in northern Wisconsin: Washington, D.C., U.S. Fish and Wildlife Service, 122 p. Abstract: Fish populations in six naturally acidic (autumnal pH 5.1-6.0) and six circumneutral (autumnal pH 6.7-7.5) clear-water lakes in north central Wisconsin were studied, and characteristics of fish populations and communities in the lakes were compared. The two groups of lakes were morphologically similar and of the same hydrologic types, but differed substantially in pH, alkalinity, waterborne calcium, and related chemical characteristics. Fish communities in the acidic lakes contained fewer species, and common as well as rare species occurred with lower frequency in the acidic lakes than in the circumneutral lakes. Keywords: Acidity, precipitation (meteorology), fishes, lakes, pollution, clarification, fresh water fishes, mathematical models, pH, alkalinity, stresses, minnows, invertebrates, growth, mercury (metal), calcium, abundance, density (mass, volume), Wisconsin, air pollution effects (animals), heavy metals