Trophic Ecology and Resource Partitioning of Common Snook and Mexican Snook in the Usumacinta River Delta

Abstract

AbstractCoexisting species often develop resource‐partitioning mechanisms to reduce their direct competition and optimize energy harvesting. Common Snook Centropomus undecimalis and Mexican Snook C. poeyi are carnivorous fish that coexist in estuaries of the Usumacinta River delta, in the southern Gulf of Mexico, and play an important role for fisheries and economy in this region. We analyzed spatial, temporal, and ontogenetic variability in trophic dynamics and distribution of Common and Mexican snooks. To identify patterns of trophic resource partitioning, we analyzed stomach content and stable isotopes (δ13C, δ15N) of the two species. Fifty‐one prey items were identified, with fish remains being the most abundant component (>35%). The two snook species appeared to be specialized carnivores of the third or fourth trophic level. Diet comparison indicated significant differences among species: Common Snook presented a higher proportion of fish from the families Engraulidae, Clupeidae, and Elopidae, while Mexican Snook consumed a higher fraction of fish from the families Cichlidae, Poeciliidae, and Loricariidae. The diet also presented significant variations between size‐classes. Small‐sized (<350 mm SL) Common Snook showed significantly higher reliance on invertebrates than large‐sized fish (>500 mm SL). Medium‐sized (351–499 mm SL) Mexican Snook consumed a higher proportion of Poeciliidae fish than small‐sized or large‐sized fish. The diet of the two snook species also presented important differences among seasons and sites. Trophic niche overlap between Common and Mexican snooks varied among systems, with higher overlap in the Pom−Atasta system than in the Palizada River. This study indicates that Common Snook and Mexican Snook have developed strategies for spatial partitioning of resources that favor their coexistence in the Usumacinta River delta.