Invertebrates, Aquatic Plants, and Waterfowl Broods on Four Selected Wetlands in St. Croix County, Wisconsin

Abstract

Two hundred forty water column invertebrate-aquatic plant samples were taken during the summers of 1983 and 1984 on 4 Waterfowl Production Areas (WPAs) in St. Croix and Polk counties, Wisconsin. Stepwise regression procedures were conducted to determine which factors were the best predictors of total invertebrate numbers and biomass. Predictors were also determined for the more common invertebrate taxa present on the study area. Detritus and duckweed (Lemna spp.) were the best predictors of total invertebrate biomass (R^2=0.293) and numbers (R^2=0.209), respectively, on Erickson WPA. On Amschler WPA, cattail (Typha spp.) and the water level were the best predictors of total invertebrate biomass (R^2=0.274) and numbers (R^2=0.181), respectively. On Flaters WPA, total invertebrate numbers were best predicted by Fries pondweed (Potamogeton friesii) (R^2=0.162). No significant (R^2>0.15) and (P<0.05) predictors of invertebrate numbers or biomass were found on Kruizenga WPA. No single predictor of total invertebrate numbers or biomass was found. In addition, predictors were different for individual invertebrate taxa, indicating a variety of aquatic plant species and growth forms are necessary to provide a variety of invertebrate food items required by ducklings.