Long-term movement patterns of a coral reef predator
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Long-term monitoring is required to fully define periodicity and patterns in animal movement. This is particularly relevant for defining what factors are driving the presence, location, and movements of individuals. The long-term movement and space use patterns of grey reef sharks, Carcharhinus amblyrhynchos, were examined on a whole of reef scale in the southern Great Barrier Reef to define whether movement and activity space varied through time. Twenty-nine C. amblyrhynchos were tracked for over 2 years to define movement patterns. All individuals showed high residency within the study site, but also had high roaming indices. This indicated that individuals remained in the region and used all of the monitored habitat (i.e., the entire reef perimeter). Use of space was consistent through time with high reuse of areas most of the year. Therefore, individuals maintained discrete home ranges, but undertook broader movements around the reef at times. Mature males showed greatest variation in movement with larger activity spaces and movement into new regions during the mating season (August–September). Depth use patterns also differed, suggesting behaviour or resource requirements varied between sexes. Examination of the long-term, reef-scale movements of C. amblyrhynchos has revealed that reproductive activity may play a key role in space use and activity patterns. It was unclear whether mating behaviour or an increased need for food to sustain reproductive activity and development played a greater role in these patterns. Reef shark movement patterns are becoming more clearly defined, but research is still required to fully understand the biological drivers for the observed patterns.
KeywordsGrey reef shark Habitat use Acoustic telemetry Activity space
This research was conducted under research permits from the Great Barrier Reef Marine Park Authority (G10/33754.1 and G10/33758.1). Funding was provided as part of a Future Fellowship (#FT100101004) to MRH from the Australian Research Council; additional funding was provided by the Australian Institute of Marine Science (AIMS). All research was conducted under James Cook University (JCU) Animal Ethics Permit A1566. Acoustic receivers utilised in this research are part of the Australian Animal Tagging and Monitoring (AATAMS) Facility of the Integrated Marine Observing System. The authors would like to thank AATAMS staff for their assistance in downloading and maintaining acoustic receivers. The authors also thank AIMS and JCU staff and students who helped with field efforts and provided assistance in obtaining IMOS data including F de Faria, L Currey, D Abdo, D Knip, M Espinoza, V Udyawer, J Matley, and A Tobin.
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