Ontogenetic stability in the trophic niche of a common Gulf of Mexico fish, Ariopsis felis

Ariopsis felis (Hardhead Catfish) is an abundant yet understudied estuarine fish species in the US Atlantic and Gulf of Mexico. Very little is known about the species’ trophic role and place in coastal food webs. This study was designed to provide baseline information on A. felis stable isotope values and to examine for any ontogenetic changes. n = 126 A. felis were sampled in the summer of 2018 in Terrebonne Bay, LA, USA, and muscle tissue was analyzed for stable carbon (δ13C) and nitrogen (δ15N) values. Overall, we found little evidence for any ontogenetic trophic niche shifts, expansions, or contractions; mature males and females have similar isotopic values and little to no differences were detected between immature and mature fish. Ultimately, A. felis occupy a trophic niche similar to that of other common estuarine fishes; however, the lack of any ontogenetic change in trophic position suggests that A. felis may be occupying a more stable and long-term place in coastal food webs.