Trophic Study of Escolar, Snake Mackerel, Lancetfish, and Oilfish in the South Atlantic Bight and Gulf of Mexico Using Stomach Content Analysis and Carbon and Nitrogen Stable Isotope Analyses

Stomach content analysis and carbon and nitrogen stable isotope analysis used in combination can provide a robust analysis of the diet and ecological role of organisms not possible for either technique used alone. This combined analysis methodology was applied to four mesopelagic teleost fishes (snake mackerel Gempylus serpens , lancetfish Alepisaurus spp. , oilfish Ruvettus pretiosus , and escolar Lepidocybium flavobrunneum ) collected from the South Atlantic Bight and Gulf of Mexico over a period of two years. These species are diel vertical migrators and the differences in the diets of these organisms is presently unknown. However, understanding their trophic role within the pelagic ecosystem is vital for on-going pelagic fisheries ecosystem modeling. Combined stomach content and stable isotope analyses were performed on these fishes and compared with species, length, weight, sex, location, and maturity. The results from the stomach content analyses show snake mackerel as having the most diverse diet and escolar having the least diverse diet. The carbon to nitrogen ratios by percent (C/N) for snake mackerel and small oilfish are characteristic of proteinaceous organisms while the higher percent C/N ratios for escolar and large oilfish are characteristic of more lipid-rich tissues. Stable isotope analyses