Variation in blacktip shark movement patterns in a tropical coastal bay

Abstract

Comparisons between shark nursery populations are limited, however recent work has shown different populations exhibit distinct space use patterns. This study examined the residency and space use of young of the year (YOY) and juvenile Australian blacktip sharks, Carcharhinus tilstoni in a northern Australian nursery using acoustic telemetry. Presence and space use patterns exhibited by C. tilstoni were highly variable among individuals. In contrast to other shark nursery populations, the majority of YOY individuals left the nursery area within three months of release, while most juveniles exhibited long-term residency (6 months - 1 year). In addition, YOY individuals used smaller amounts of space than juveniles. Variable activity space size and location indicated individuals used different areas and often moved into new areas. High individual variation in juvenile populations is atypical for carcharhinid sharks, and contrasts with other nursery species, including the common blacktip shark C. limbatus, which are known to exhibit residency and consistent space use patterns in nursery areas. The unique patterns observed among C. tilstoni may be due to a number of factors, including differences in nursery habitat and population structure, or strategies to improve survival. This study highlights the importance of investigating nursery behaviour across different habitats and populations.