Linking Ontogenetic, Seasonal, and Spatial Variability in the Trophic Biology of Citharichthys spilopterus to Environmental Conditions in a Tropical Estuary

The flatfish Citharichthys spilopterus is a common predatory species in the estuaries of the southwestern Gulf of Mexico. In general, factors controlling the foraging behavior of fish can be extrinsic (environmental conditions) or intrinsic (size-related differences). The main objective of this study was to analyze spatiotemporal and body size-related variations in the diet of this species and their coupling with main environmental conditions. Every two months, 24 h sampling cycles were conducted in two habitats, one with submerged vegetation and the other without vegetation. Fish were collected every 2 h during each cycle. Canonical correspondence analysis revealed that submerged vegetation and body size were the main factors influencing diet composition, while diurnal variation was not significant. Decapod larvae and copepods were consumed more frequently in the unvegetated habitat during the dry season and by smaller fish, while peracarids, shrimp, and fish were consumed more frequently in the vegetated habitat during the rainy season and by larger fish. PERMANOVA analysis detected significant differences in diet between size groups, habitats, and months. Similarly, the fullness index showed significant differences between size groups and months. These spatiotemporal and ontogenetic trophic changes reflect the adaptation processes of the species to the seasonal and spatial environmental variability of the system.