Trophic Relationships and Niche Partitioning of Red Drum Sciaenops ocellatus and Common Snook Centropomus undecimalis in Coastal Estuaries of South Florida

摘要

Large marine predators occupying the same spatial arena exhibit a variety of temporal and behavioral differences to minimize competition for habitat and prey. Here, we examined two such species in the Florida Everglades, red drum Sciaenops ocellatus and snook Centropomus undecimalis, to evaluate niche separation based on diet and multiple stable isotope (white muscle, C-13, N-15, S-34) analyses. For these two estuarine predators, our results indicated that although dietary niche overlap was broad, different feeding modes (spatial and behavioral) allow niche partitioning. The diet of red drum was dominated by pink shrimp Farfantepenaeus duorarum and other demersal species. For snook, although their diet included significant numbers of pink shrimp, it was largely dominated by pelagic and epibenthic fishes. Mean red drum C-?13 signatures (-10.5 to -20.8 parts per thousand) differed significantly between areas and were strongly correlated with both area-specific seagrass concentration and amount of incidental seagrass ingestion. Mean snook C-13 signatures were generally depleted (-20.9 to -22.4 parts per thousand) with the exception of one area (-14.1 parts per thousand). Red drum and snook diet and mean N-15 signatures (10.1 parts per thousand, 10.8 parts per thousand, respectively) indicated they were both mid-trophic-level consumers. Mean red drum S-34 signatures were significantly depleted (-0.31 parts per thousand) in the seagrass-dominated area, but enriched (2.03 to 3.78 parts per thousand) in the other areas and indicated benthic but no pelagic sources of primary production. Mean snook S-34 signatures varied widely (0 to 20 parts per thousand) among areas suggesting dependence on benthic (benthic algae and seagrass) and pelagic (phytoplankton) sources of primary production.