Distribution, abundance, social and genetic structures of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Perth metropolitan waters, Western Australia
In heterogeneous coastal and estuarine environments, dolphins are exposed to varying levels of human activities. Consequently, it is important to identify and characterise fine-scale population structuring based on ecological, social, spatial and genetic data to develop appropriate conservation and management strategies. This thesis focused on identifying subpopulations of Indo-Pacific bottlenose dolphins (Tursiops aduncus) inhabiting Perth waters, Western Australia (WA). Using spatial and social data collected over four years of boat-based photo-identification surveys, I: i) estimated abundances, survival and movement rates using a Multistate Closed Robust Design approach; and ii) examined the social structure and home range using social association and network analyses. I used microsatellite loci and mtDNA markers to investigate the genetic population structure of dolphins at metropolitan (Perth) and regional (c. 1000 km of coastline) scales. High capture probabilities, high survival and constant abundances described a subpopulation with high fidelity in an estuary. In contrast, low captures, emigration and fluctuating abundances suggested transient use and low fidelity in an open coastline region. Overall, dolphins formed four socially and geographically distinct, mixed-sex subpopulations that varied in association strength, site fidelity and residency patterns. Curiously, home range overlap and genetic relatedness did not affect the association patterns. In Perth metropolitan waters, a source-sink relationship was suggested between a subpopulation inhabiting a semi-enclosed embayment and three other subpopulations, including the estuarine subpopulation. On a broader scale, the Perth metapopulation was genetically distinct from other populations along the WA southwestern coastline, with little to no migration from and into other populations. The subpopulations present in Perth waters should each be regarded as a distinct management unit, with a particular focus on protecting the estuarine subpopulation, which is small, has limited connection with adjacent subpopulations and is more vulnerable because of the intensity and diversity of anthropogenic threats present in the estuary
