First trophic ontogeny data for the scalloped bonnethead Sphyrna corona in the Colombian Pacific

Ontogenetic shifts in habitat use and diet provide key insights into the ecological requirements of species throughout their life cycle. The scalloped bonnethead shark Sphyrna corona is a Critically Endangered hammerhead shark, yet little is known about its biology and trophic ecology. This study describes the feeding ontogeny of S. corona in the central Colombian Pacific using stable isotope analysis in vertebrae. A total of 11 individuals collected in 2022 yielded 24 subsamples with δ 13 C values characteristic of coastal habitats (-15.2 to -12.9‰). Size classes defined by vertebral radius (VR) included small (1.14-1.86 mm VR), medium (2.46-2.92 mm VR), and large (3.00-5.58 mm VR) individuals. δ 13 C signatures were less enriched in small (-14.4 ± 0.17‰) and medium (-14.4 ± 0.19‰) individuals than in large individuals (-13.3 ± 0.12‰), suggesting shifts in habitat use or prey sources with growth. δ 15 N values (9.5-13.0‰) were similar among size classes (11.3 ± 0.26‰, 10.1 ± 0.23‰, 10.7 ± 0.17‰), corresponding to trophic positions between 3.1 and 5.2. Isotopic niche width varied from narrow (SEA C : 0.54‰ 2 ) to broad (2.03‰ 2 ), with moderate to high niche isotopic overlap among size classes. Bayesian mixing models indicated a diet dominated by crustaceans (53.5%), followed by coastal pelagic fish (15.8%), coastal squid (10.4%), benthopelagic fish (7.8%), and benthic fish (5.7%). These results identify S. corona as a coastal mesopredator and crustacean specialist in the central Colombian Pacific, providing the first trophic ontogeny data for this endangered species.