Atlantic Tarpon (emMegalops Atlanticus/em) Exhibit Upper Estuarine Habitat Dependence Followed by Foraging System Fidelity After Ontogenetic Habitat Shifts

Fish can have complex life histories and use multiple habitats and resources during different life stages. Consequently, their complete life histories are often poorly understood. Atlantic Tarpon (Megalops atlanticus) is an ecologically and economically important sport fish, yet little is known about its lifelong habitat and resource use. We used stable isotope analysis of eye lens δ13C and δ15N to explore patterns in trophic history and habitat use of 16 Atlantic Tarpon from west-central Florida and Louisiana. The stable isotope chronologies indicated dependence on upper estuarine habitats during the early life history, and an ontogenetic shift to coastal waters at approximately 10 years of age and 140 cm total length. During the coastal phase, Atlantic Tarpon displayed among-individual variability and within-individual consistency in basal-resource dependence. Our study highlights the importance of upper estuarine habitats to the early life stages of Atlantic Tarpon, as well as the possibility that adults show fidelity to coastal systems for feeding and growth.