Exploring the trophic strategies of two large pelagic species inhabiting the Galapagos Marine Reserve

We explored the trophic strategies of the broadbill swordfish (Xiphias gladius) and dolphinfish (Coryphaena hippurus) within the Galapagos Marine Reserve (GMR), using stable isotope analysis to infer habitat use and their trophic interactions. Muscle tissue samples were collected after the seizure of an illegal fishing boat in 2018. We observed interspecific differences in δ¹³C and δ¹⁵N signatures, suggesting different feeding patterns between species. X. gladius exhibited a broader isotopic niche and higher trophic position, which could be associated with greater trophic flexibility and consumption of demersal and mesopelagic prey. In contrast, C. hippurus displayed a narrower isotopic niche and a lower trophic level, suggesting a more restricted diet focused on small epipelagic prey. Trophic niche partitioning between these two species would be an ecological mechanism aimed at reducing competition and facilitating their coexistence in the region. Our findings highlight the importance of the GMR as a buffer area and feeding ground for large commercially pelagic species in the Eastern Tropical Pacific.