Movement and population dispersal of dolphinfish (Coryphaena hippurus) across the Eastern Tropical Pacific inferred from carbon and nitrogen stable isotope analyses

The dolphinfish (Coryphaena hippurus) is a globally distributed marine predator that supports one of the most important coastal fisheries along the Eastern Tropical Pacific (ETP), but its spatial movements in this area are poorly understood. Stable isotope values (δ¹³C and δ¹⁵N) of white muscle from dolphinfish (n = 220) captured at different locations across the ETP (i.e., Mexico, Costa Rica, Ecuador, Peru and oceanic areas) were normalized to copepod baseline stable isotope values to estimate dolphinfish trophic position, movements and population dispersal. Movement or residence patterns were inferred from the difference in δ¹⁵N values (Δ¹⁵N_{dolphinfish-copepod}‰) between copepods and dolphinfish muscle. Baseline corrected isotope values (δ¹³C_{dolphinfish-copepod} and δ¹⁵N_{dolphinfish-copepod}) of dolphinfish muscle were used to estimate isotopic niche metrics and infer population dispersal across isoscapes. Values of δ¹³C and δ¹⁵N differed between juvenile and adult dolphinfish and across the ETP. Trophic position estimates ranged from 3.1 to 6.0 with a mean of 4.6. Adults and juveniles had similar trophic position estimates, whereas isotopic niche areas (SEA ‰²) of adults were greater relative to juveniles in every location. Adult dolphinfish showed “moderate movement by some individuals” in all locations based on Δ¹⁵N_{dolphinfish-copepod} values, except for Costa Rica where adults were classified with “high degree of movement by some individuals” whereas juveniles showed “limited movement” in all areas except Mexico. Population dispersal based on Δ¹⁵N_{dolphinfish-copepod} values showed “moderate” and “high” dispersal for adults and “no dispersal” for most juveniles, except for Mexico. This study provides insight into potential dolphinfish spatial mobility across an area of interest for multiple nations, which can help to improve stock assessments and management of the species.