Abstract
Intrinsic tracers, such as stable isotopes of carbon and nitrogen, are common dietary markers that accumulate in the muscle tissue of consumers and can be used to determine the dietary sources and trophic positions of consumers. The aim of this study was to assess regional variation in the trophic ecology of wahoo (Acanthocybium solandri) using bulk stable isotopes. Muscle biopsies of wahoo were collected from four regions in the western Atlantic Ocean: the eastern Gulf of Mexico, western Gulf of Mexico, Northwest Atlantic Ocean, and Caribbean Sea. Muscle tissue δ13C and δ15N values for wahoo ranged from −15.8‰ to −18.8‰ and from 7.2‰ to 12.8‰, respectively. Wahoo collected in the Caribbean Sea displayed the highest mean δ13C value (−16.3‰), and individuals from this region were statistically different from the three other regions sampled. Mean δ15N values were elevated for wahoo collected in the eastern and western Gulf of Mexico (11.4‰ and 11.1‰, respectively), and the values were over 2‰ higher than samples from the Northwest Atlantic Ocean and Caribbean Sea. Trophic position (TP) was estimated using δ15N baselines (zooplankton) and δ15N wahoo values for each region, and mean TP was 0.4 to 0.9 higher in the Caribbean Sea relative to the three other regions, suggesting that wahoo in this region feed on higher-trophic-level prey. The results indicate that δ15N baselines and the trophic positions of wahoo each vary as a function of their geographic location, which supports the hypothesis that this species feeds opportunistically throughout its range.