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Whole body concentrations of Cd, Cr, Cu, Fe, and Zn were determined for samples of chain pickerel (Esox niger), bluegill (Lepomis macrochirus), blueback herring (Alosa aestivalis), brook silverside (Labidesthes sicculus), and golden shiner (Notemigonus crysoleucas) from a 1,120-hectare impoundment near Aiken, South Carolina. Species differences in mean concentrations were found for all five elements. Frequency distributions of 23 species-element groupings were compared to the normal, lognormal, Weibull, and exponential distributions. The lognormal, normal, Weibull, and exponential distributions had the best fit to 57, 17, 26, and 0 percent of the species-element groupings, respectively. Four of the 23 species-element groupings departed significantly from all four of the distributions, primarily as a result of strong positive skewness. All species for which Cd and Cr were studied exhibited significant positive skewness, while skewness was less pronounced for concentrations of Cu, Fe, and Zn. Most samples to which the Weibull distribution gave the best fit did not depart significantly from either the lognormal or normal distribution. Therefore, in most cases either the normal or lognormal distribution may be satisfactorily employed as statistical models of frequency distributions of trace metal concentrations in fishes. Known required elements (Cu, Fe, and Zn) tended more towards normality than Cd and Cr, which followed lognormal distributions.
Giesy et al. (Fri,) studied this question.