Patterns in the Abundance and Composition of Fishes among Beds of Different Macrophytes: Viewing a Littoral Zone as a Landscape

Abstract

To determine if the density, biomass, species density (number of fish species per square metre), and species composition of juvenile and forage fish (fish ≤ 100 mm SL) differed among macrophyte types, we sampled fishes monthly from beds of Hydrilla verticillata, Panicum hemitomon, and Potamogeton illinoensis in two areas of Lake Okeechobee, Florida, from December 1989 to December 1990. Fish density and biomass differed significantly among the three macrophytes despite our design having relatively low statistical power to detect such differences. Densities and biomass were highest in H. verticillata (196 fish∙m−2, 30 g∙m−2), intermediate in P. hemitomon (60 fish∙m−2, 12 g∙m−2), and lowest in P. illinoensis (31 fish∙m−2, 6 g∙m−2). Trends among macrophytes were consistent throughout the year despite significant variation among months. Fish species density did not vary significantly among macrophyte types. However, the relative abundances of fishes differed significantly among macrophyte types. Patterns in fish abundance and relative species composition led us to infer that beds of different macrophyte types constitute distinct microhabitats for fish and structure the littoral zone of Lake Okeechobee into a mosaic landscape.