Movements and trophic ecology of dolphinfish (Coryphaena hippurus) in the Mexican Central Pacific inferred from stomach content, bulk, and compound-specific stable isotope analyses

Feeding habits and habitat use inform ecosystem-based management strategies for commercial fish species. A consumer’s diet can be assessed through stomach content analysis (SCA), bulk stable isotope analysis (BSIA) and compound-specific stable isotope analysis of amino acids (CSIA-AA). Our research establishes the first approach combining these traditional and novel techniques to provide insight on the movements and trophic ecology of dolphinfish (Coryphaena hippurus) in the Mexican Central Pacific (MCP) during 2013. Dolphinfish SCA (n = 311), muscle δ ¹⁵N and δ ¹³C BSIA (n = 148), and δ ¹⁵N CSIA-AA (n = 9) were performed to assess trophic and movement patterns. Diet was composed of 59 prey items. According to the Prey-Specific Index of Relative Importance, the main prey were Argonauta spp. (24%), Portunus xantusii (11%), Dosidicus gigas (7%), and Selar crumenophthalmus (7%). Diet differed between seasons and age class but not by sex. Trophic position did not change with body size based on SCA or SIA with average estimates of 3.5, 4.1, and 4.3 based on BSIA, CSIA, and SCA, respectively. Adult dolphinfish showed a shift in their isotopic niche; bulk δ ¹⁵N values varied widely in adults (⁓ 10‰) suggesting movements through different isoscapes while juveniles had more constrained values consistent with residency within the regional isoscapes. These results were supported by differences in source amino acid δ ¹⁵N mean values between juveniles (4.6‰) and adults (0.8‰). Our findings suggest that the MCP is a migration corridor for dolphinfish between foraging areas across the Eastern Tropical Pacific.