Semester of Graduation

Spring 2020


Master of Science (MS)


Oceanography and Coastal Sciences

Document Type



Niche partitioning, the process by which competing species use different subsets of the available resources, is commonly used to explain the coexistence of closely related species. In the northwest Gulf of Mexico on the shelf-edge banks, red snapper (Lutjanus campechanus) and vermilion snapper (Rhomboplites aurorubens) are two coexisting closely related species. Yet, little is known about how these species partition resources. In this study, niche partitioning of red snapper and vermilion snapper was investigated using gut contents and stable isotopes. While dietary niche partitioning was apparent, the species relied upon similar prey and displayed isotopic niche overlap, supporting the notion that their resource use overlaps. Red snapper and vermilion snapper shared five of the seven broad prey categories. Isotope niche overlap between the species was approximately 10%, with the greatest overlap occurring between the largest vermilion snappers (≥300 mm) and red snappers species’ diets was the predominance of fish and zooplankton. Red snapper specialized on fish, whereas vermilion snapper specialized on zooplankton. Vermilion snapper exhibited lower ∆13C and ∆15N values relative to red snapper, which is indicative of greater pelagic feeding on lower trophic level prey. The degree of niche partitioning was similar across different locations; however, size-related niche shifts were not consistent. It is possible that niche partitioning is the result of long-standing competition occurring between red snapper and vermilion snapper. In addition, size-related niche shifts might reduce intraspecific competition. However, competition is unlikely to occur unless shared food resources are limited. Further research is required to determine the existence of competition. Understanding interactions among coexisting species can provide a framework for a multispecies management approach.

Committee Chair

Cowan, James

Available for download on Tuesday, March 16, 2021