Quantitative assessment of benthic food resources for juvenile Gulf sturgeon,Acipenser oxyrinchus desotoi in the Suwannee River estuary, Florida, USA

Abstract

Gulf sturgeon,Acipenser oxyrinchus desotoi, forage extensively in the Suwannee River estuary following emigration out of the Suwannee River, Florida. While in the estuary, juvenile Gulf sturgeon primarily feed on benthic infauna. In June–July 2002 and February–April 2003, random sites within the estuary were sampled for benthic macrofauna (2002 n = 156; 2003 n = 103). A mean abundance of 2,562 ind m−2 (SE ± 204) was found in the summer, with significantly reduced macrofaunal abundance in the winter (mean density of 1,044 ind m−2, SE ± 117). Benthic biomass was significantly higher in the summer with an average summer sample dry weight of 5.92 g m−2 (SE ± 0.82) compared to 3.91 g m−2 (SE ± 0.67) in the winter. Amphipods and polychaetes were the dominant taxa collected during both sampling periods. Three different estimates of food availability were examined taking into account principal food item information and biomass estimates. All three estimates provided a slightly different view of potential resources but were consistent in indicating that food resource values for juvenile Gulf sturgeon are spatially heterogeneous within the Suwannee River estuary.