Movement patterns of juvenile blacktip sharks (Carcharhinus limbatus) within a tropical nursery habitat
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2025-05
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Abstract
Blacktip sharks (Carcharhinus limbatus) are a circumglobal species that rely on nearshorenursery habitats during their early years. Very little is known of the movement patterns and habitat usage of blacktip sharks in the Hawaiian Islands, and no nursery habitats have yet been designated for this species within Hawai‘i. For this study, juvenile blacktip sharks (n = 29) were caught and tagged in Hilo Bay, Hawai‘i, USA, using VEMCO V-13 PPM acoustic transmitters. Tracking occurred every 2-5 weeks between July 2022 and January 2024 at 44 stations throughout Hilo Bay using a VR-100 receiver and VH-165 omnidirectional hydrophone. Results showed that juvenile blacktip sharks were present in the Bay year-round with peak occurrence of tagged individuals (41.3-50.0%) between March and August, and more limited occurrence (24.1-30.1%) between October and January. Tagged sharks were detected within Hilo Bay more during the day than at night, likely due to excursions into deeper waters during heightened nocturnal foraging activity. Accordingly, blacktip sharks were detected more frequently in deeper waters at night. Detections were significantly higher in areas where the benthic composition was predominately mud as opposed to coral or rock. Temperature and salinity did not significantly vary among stations, and as such, were not influential factors in habitat use, though DO appeared to limit habitat use during the day when concentrations were lowest. Thus, juvenile blacktip sharks appear to preferentially utilize deeper habitats with mud substrates within Hilo Bay and are limited in these areas by DO. The lowest levels of DO were recorded during the months with the fewest sharks detected in the Bay, suggesting that oxygen requirements may be limiting both spatial and temporal habitat usage. The results presented here are the first to delineate Hilo Bay as a blacktip shark nursery habitat in Hawaiian waters and suggest that this population of blacktip sharks resides predominantly within Hilo Bay for the first few years of their life.
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Conservation biology, Zoology, acoustic telemetry, diel, distribution, Hawai‘i, site fidelity, temporal
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39 pages
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