Variation in habitat use and trophic dynamics of a catadromous fish (Anguilla rostrata) in sub-tropical Texas

American Eel is an economically, ecologically, and culturally valuable fish. Increased fishing pressure and other stressors have earned international threatened and endangered designations in an effort to protect the species. U.S. Fish and Wildlife Service (USFW) species status reviews resulted in no protection for the species in the U.S. due partly to data gaps about the dynamics of facultatively catadromous strategies and migratory plasticity of the species. The outcome of the reviews has led to questions about the species in lesser-known regions of its range resulting in the creation of a multi-tiered project to assess population structure, distribution, habitat use, and parasite affliction of Gulf of Mexico (GOM) eels, specifically in Texas. For this study, American Eel were caught in different hydrological systems in Texas from 2012 – 2019. Muscle tissue stable isotope analyses (SIA) of δ13C, δ15N, and δ34S were used to elucidate habitat use and trophic ecology. SIA is widely used for studies focused on food web interactions and has seen increased interest in elucidation of migratory histories. Isotopic values differing across salinity gradients are reflected in primary producers and then assimilated in the tissues of consumers. Individuals were sampled from river and coastal basins in Texas from 2009 to 2019. Univariate and multivariate analysis revealed that individuals displayed highly variable isotopic values both within and between major hydrologic system groups, perhaps suggesting differences in life history strategies that could fill in a gap in knowledge of the species in this lesser-known region of its range.