Long-term abundance, residency patterns and habitat use of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Byron Bay, Australia

Context The assessment of population abundance, dynamics and spatial use of coastal dolphins is essential for guiding conservation management measures. Aim This study investigated the long-term abundance, site fidelity, residency patterns and habitat use of Indo-Pacific bottlenose dolphins (Tursiops aduncus) within the Cape Byron Marine Park. Methods Photo-identification data collected from 115 vessel-based surveys (591 h) between 2003 and 2023 were used to assess population structure and areas of core use. Key results The population was composed of a high proportion of transients (59.9%; n = 659), alongside individuals exhibiting varying degrees of site fidelity. Four residency clusters were identified, including a core community with multi-decadal presence, reaching a maximum abundance of 62.2 individuals (95% CI = 54.51–71.05) in 2014. Non-resident abundance peaked at 411.4 (95% CI = 382.86–442.02) in 2014. Spatial analysis showed long-term consistency in the use of core habitats. Conclusions Population densities in the study area appear among the highest reported for the species in Australia and, together with the long-term use of critical habitat areas, highlight the region’s high conservation value. Implications The findings from this study have important implications for the management of the marine protected area and enhance the limited knowledge of this species along the eastern coast of Australia.