Regional Variation in the Trophic Ecology of Wahoo (Acanthocybium solandri) in the Western Atlantic Ocean

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 delta C-13 and delta N-15 values for wahoo ranged from -15.8 parts per thousand to -18.8 parts per thousand and from 7.2 parts per thousand to 12.8 parts per thousand, respectively. Wahoo collected in the Caribbean Sea displayed the highest mean delta C-13 value (-16.3 parts per thousand), and individuals from this region were statistically different from the three other regions sampled. Mean delta N-15 values were elevated for wahoo collected in the eastern and western Gulf of Mexico (11.4 parts per thousand and 11.1 parts per thousand, respectively), and the values were over 2 parts per thousand higher than samples from the Northwest Atlantic Ocean and Caribbean Sea. Trophic position (TP) was estimated using delta N-15 baselines (zooplankton) and delta N-15 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 delta N-15 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.