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Dolphins as part of the ecological character of Ramsar-listed wetlands: A case study of Indo-Pacific bottlenose dolphins in the Peel-Harvey Estuary, Western Australia

Nicholson, Krista (2021) Dolphins as part of the ecological character of Ramsar-listed wetlands: A case study of Indo-Pacific bottlenose dolphins in the Peel-Harvey Estuary, Western Australia. PhD thesis, Murdoch University.

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Abstract

Whether dolphins are part of the ecological character of Ramsar-listed wetlands depends on their status as a biological component of the ecosystem (e.g., dolphin biomass, residency) and their involvement in ecosystem processes (e.g., energy and nutrient dynamics, species interactions). The aim of this thesis is to provide the scientific basis for deciding whether Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the Peel-Harvey Estuary (PHE) in Western Australia should be considered part of the ecological character of the Ramsar-listed Peel-Yalgorup wetland system that the PHE is a part of. Dolphin photo-identification and behavioral data, as well as tissue samples, were collected during boat-based surveys in the PHE and adjacent coastal waters between 2016 and 2019. Social, spatial and isotopic (δ13C and δ15N) niche partitioning were investigated to identify population structure based on biologically meaningful criteria. Social structure, home range and stable isotope analyses confirmed a year-round resident, socially, spatially and isotopically distinct community of ~90 dolphins occupying the PHE. The estuarine community had a slightly negative population growth rate (-0.004, SD 0.062) with a low probability (0.010, SE 0.003) of extinction in 100 years. The community was closed to immigration, with changes in abundance driven by births and deaths and likely permanent emigration of immature males. Social clusters within the community were heterogeneous in their space use and diet. Detritivores, omnivores and herbivores and benthic omnivores and carnivores each contributed approximately a third and water column species 10%, to the annual fish biomass (~200,000 kg) removed by the resident dolphin community. The findings of this thesis provide strong empirical evidence that dolphins are functional biological components of the ecological character of the Peel-Yalgorup Ramsar site.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): Environmental and Conservation Sciences
United Nations SDGs: Goal 14: Life Below Water
Supervisor(s): Loneragan, Neil, Bejder, Lars and Finn, Hugh
URI: http://researchrepository.murdoch.edu.au/id/eprint/62546
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