An index of biotic integrity: A test with limnological and fish data from sixty Florida lakes

An index of biotic integrity (IBI) that used eight fish assemblage metrics was examined for effectiveness in estimating anthropogenic impacts to 60 Fl orida lakes ranging in size from 2 ha to more than 12,400 ha. The lakes ran ged in trophic status from oligotrophic to hypereutrophic and had aquatic m acrophyte abundances (percent lake volume infested) ranging from less than 1% to 100%. Fish species were classified by trophic feeding guild and toler ance to increases in turbidity or warming and decreases in dissolved oxygen concentration. Fish assemblage metrics tested were as follows: number of f ish species, number of native fish species, number of Lepomis species, numb er of piscivorous species, number of generalist species, number of invertiv ore species, number of species intolerant of increased turbidity or warming and decreased dissolved oxygen concentration, and number of species tolera nt of increased turbidity or warming and decreased dissolved oxygen concent ration. The total IBI scores and the data used to calculate individual metr ics were unable to accurately predict the degree of anthropogenic impact to 60 Florida lakes, as estimated by personal observations of local limnologi sts, lake chloride concentrations. and road densities in the watersheds. La ke surface area and lake trophic status have a dominant influence on the fi sh assemblage metrics tested in this study. Thus, the IBI approach may be o f limited usefulness for predicting anthropogenic impact in lake data sets that have wide ranges of surface areas and trophic status classifications.