Seasonal and Ontogenetic Variation in the Diet and Daily Ration of Estuarine Red Drum as Derived from Field‐Based Estimates of Gastric Evacuation and Consumption

Abstract

AbstractThe application of ecosystem‐based approaches in fisheries management has been limited by a lack of empirical data for quantifying the ecological interactions among many common and valuable fishery species. The red drum Sciaenops ocellatus, a large, carnivorous member of estuarine communities, is experiencing population recovery throughout its range in the U.S. South Atlantic and Gulf of Mexico. Using a field‐based approach, we determined seasonal and ontogenetic variation in the contribution of valuable fishery resource species to red drum diets, estimated red drum daily ration, and quantified per capita and population‐level predation by juvenile and subadult red drum in a North Carolina estuarine system. Despite seasonal, interannual, and ontogenetic variation in diet composition, red drum fed mainly on macrocrustaceans and juvenile fishes, including several economically important resource species (e.g., blue crab Callinectes sapidus, penaeid shrimp, and Atlantic menhaden Brevoortia tyrannus). Both juvenile and subadult red drum demonstrated strong diel feeding patterns, with peak feeding occurring during the hours just after dark. Gastric evacuation rates during periods of declining gut fullness were estimated on seven sampling dates and produced mean daily ration estimates between 1.2% and 3.4% of predator mass depending on age‐group. Combining field‐observed red drum growth rates with published laboratory estimates of gross growth efficiency suggested that our estimates of daily ration were likely biased low. During the seasonal period of rapid growth, the aggregate consumption of blue crabs, penaeid shrimp, and Atlantic menhaden by juvenile and subadult red drum in North Carolina waters was estimated at 3.4 × 106 to 5.1 × 106 kg/year.Received October 12, 2011; accepted May 24, 2012