High residency of a Critically Endangered hammerhead shark to a small area: implications for marine protected area management and design

Hammerhead sharks are among the most iconic and threatened shark species. Research has focused on the large hammerhead species, with relatively little work conducted on their smaller-bodied relatives, which face many of the same threats. One such species, the scalloped bonnethead Sphyrna corona, is assessed as Critically Endangered by the IUCN Red List; however, there is no knowledge about its movements, which can compromise management and conservation efforts. Here, we used acoustic telemetry to describe the spatiotemporal movements of scalloped bonnetheads inside a national park’s marine protected area along the Colombian Pacific coast, where this species still occurs in high numbers. The movements of 25 adult sharks were monitored over a 1.4 km2 area for up to ~10 mo between 2022 and 2023. Scalloped bonnetheads exhibited high residency to the area (RImax = 0.78 ± 0.18, RImin = 0.59 ± 0.32, ±SD), with most sharks present during the majority of their monitoring period. Shark movements were influenced by tides and diel period, and the space sharks used was generally small (mean 50% utilization distribution: 0.3 ± 0.2 km2), with most of their movements detected by 2 (out of 5) receivers separated by less than 2 km. These results indicate that scalloped bonnetheads spend a large amount of time in a small area, suggesting that even a spatially limited no-take zone in the National Natural Park is likely to benefit the conservation of this species. This study provides the first insights into the movement behavior of the scalloped bonnethead, with important information for its protection and management.