Movement patterns and residency of silvertip sharks (Carcharhinus albimarginatus) in a remote archipelago of the Eastern Tropical Pacific

Abstract

The silvertip shark (Carcharhinus albimarginatus) is a reef-associated shark widely distributed across the Indo-Pacific. However, it has been poorly studied and little is known about its spatial ecology, particularly about long-range travels. In this study, we investigated the residency and movement patterns of silvertip sharks in a widespread remote archipelago offshore the Pacific coast of Mexico, the Revillagigedo Archipelago. An array of 10 VR2W receivers was deployed around the archipelago to monitor the movement of 45 silvertip sharks during 11 years. Among the 40 sharks detected during the study, 34 exhibited high site fidelity with 70% of their daily detections recorded in one particular site. Residency index ranged from 0.049 to 0.99 with an average residency of 0.49 ± 0.27 (SD). The sharks exhibited strong diurnal patterns in horizontal and vertical movements with two peaks of detections at sunrise and sunset and a presence in deeper waters during daytime. Eleven individuals (7 adult females) traveled from one island to another (separated by distances ranging from 60 to 425 km). Geographical ontogenetic segregation was observed within the archipelago with juveniles being present only around San Benedicto and Socorro islands. Five sharks tagged as juveniles left their tagging island once they had reached adulthood, three males between 8 and 10 years old and two females at 11 years old.