Stable isotope evidence for movements of hammerhead sharks Sphyrna lewini, connecting two natural protected areas in the Colombian Pacific

Coastal areas are particularly important, as their shallow waters commonly correspond to nursery areas for many species. Unfortunately, these habitats also support many commercial fisheries which overlap with nursery areas and can represent a risk to numerous shark species, including Sphyrna lewini which frequent both coastal waters and offshore islands throughout their lifecycle and are affected by the high fishing activity in coastal areas, particularly during their early life stages. For this reason, it is imperative to identify and establish connectivity between key habitats during their lifecycle to improve conservation strategies. This study provides the first evidence about habitat use and migration corridors between oceanic aggregation zones and coastal areas of the Colombian Pacific, which constitute important habitats for S. lewini. A total of five S. lewini neonates were sampled in the Sanquianga National Natural Park coastal area: the individuals ranged from 48.2 to 52.8 cm in total length and were obtained by artisanal fishermen. Our δ13Ccorrected (− 16.3 ± 0.16‰) and δ15N (15.9 ± 0.11‰) values were similar to those obtained from specimens from the Malpelo isospace (δ13C: − 16.3 ± 0.1‰ and δ15N: 15.9 ± 0.11‰). Our isotopic results showed significant use and connectivity between both marine environments (oceanic and coastal areas), the extent of which depended on shark maturity stages, providing evidences of the trophic links of S. lewini between Malpelo waters and the Sanquianga National Natural Park coastal area. Therefore, this study highlights the importance of both habitats in the lifecycle of S. lewini and provides preliminary inferences about S. lewini ecology and habitat preference representing a baseline for further research.