Stable Isotopic Niche Variability and Overlap across Four Fish Guilds in the North‐Central Gulf of Mexico

The quantification of niche diversity and overlap is useful for understanding the impacts fisheries regulation management. In this work, we evaluate isotopic size at guild species levels. Specifically, analyzed guild- species-specific space using SIBER nicheROVER packages, evaluated length-specific geographic contrasts in isotopes fishes north-central Gulf Mexico. Stable carbon nitrogen isotope values (δ13C δ15N) fish were compared among four ecotype-based guilds: estuarine, coastal migratory pelagic (CMP), reef, large offshore (LOP). Significant differences mean stable found guilds. Estuarine exhibited highest δ13C variability, Red Drum Sciaenops ocellatus most isotopically diverse. Variability CMP was comparable to that some estuarine species, whereas reef LOP less variable. Fishes within had largest δ15N range. Reef smallest consistently largest, although no any occupied as an Drum. Distinct well-separated niches also observed between species; however, high We a positive relationship TL Drum, Blackfin Tuna Thunnus atlanticus, Yellowfin T. albacares, Snapper Lutjanus campechanus showed distinct areas. This study provides data not only on how without ecotypes interact but variability their interactions, all which can inform ecosystem-based management models.