The diets of a transitory fish (spotted sea trout, Cynoscion nebulosus) and a fish with presumed greater site-fidelity (pinfish, Lagodon rhomboides) were analyzed with respect to habitat. Sampling occurred in Barataria Bay, Louisiana between May 2003 and May 2004. Spotted sea trout were caught using gillnets, and pinfish were caught using baited fish traps. Each gear was used on three habitats: mud bottom, oyster shell, and marsh edge. In addition, sampling for spotted sea trout was repeated at three locations along a salinity gradient. A total of 175 spotted sea trout stomachs and 137 pinfish stomachs were examined.
Seventeen prey species were identified in the guts of spotted sea trout, and thirteen species were identified for pinfish. Fifty-three percent of spotted sea trout stomachs were empty, and 37% of pinfish stomachs were empty. Unidentifiable fish and brown shrimp(Farfantepenaeus aztecus) were consistently the most important prey items for spotted sea trout in weight, frequency, and caloric value. Plant material, detritus, and small amounts of fish and shrimp, were consistently most important for pinfish by weight, frequency, and caloric value. The diet of spotted sea trout caught adjacent to marsh edge had the least dietary overlap with fish from other habitats, especially during winter and spring. The diet of pinfish caught over shell had the least dietary overlap with conspecifics from other habitats. Dietary breadth for spotted sea trout was similar across habitats and lowest in winter. Dietary breadth for pinfish was lowest on the shell habitat and in fall. Neither habitat, season, water quality (i.e., dissolved oxygen, temperature, salinity), nor any other effect could be shown to be statistically significant in distinguishing the diet of either fish using Analysis of Variance (ANOVA) and Analysis of Similarities (ANOSIM) statistical techniques.
Diets of these two fish were not notably diverse, but the dietary breadth for both fish species was high, suggesting that of those prey items consumed, there was no strong preference among the prey. This may be attributable to the transitory nature of the fish and the ubiquity of some of the prey types across habitat types.