Nahiid Stephens

An investigation into the deaths of six Indo-Pacific bottlenose dolphins (Tursiops aduncus) within the Swan Canning Riverpark between May-October 2009 found that a suite of factors likely contributed to the mortalities (Beazley 2010; Holyoake et al. 2010). This investigation, along with research undertaken for Swan Canning Research Innovation Program (SCRIP) Project: ―Toxicant exposure, population genetics, and trophic associations of bottlenose dolphins (Tursiops sp.) in the Swan River‖ (Holyoake et al. 2011), emphasised the vulnerability of the resident community to natural and anthropogenic stressors and the need to improve the scientific basis for the long-term conservation of dolphins within the estuary. To support this aim, the Swan River Trust and Murdoch University entered into a collaborative agreement Project to undertake further health and ecology investigations into dolphins in the Swan Canning Riverpark and to conclude analyses of existing data and samples. This report presents the major findings for this project.

Since 2008 an unprecedented number of humpback whales (Megaptera novaeangliae) have stranded in Western Australia (WA). Between 1989 and 2007 the mean number of humpback whales ashore was between 2 and 3 animals (range: 0-5). In 2008 there were 13 strandings followed by 46 in 2009 and 16 in 2010. The aim of this project was to initiate the collection of data by post-mortem examination of stranded whales in 2011 in order to: 1) identify and characterise factors associated with strandings; and 2) determine baseline and epidemiological information on disease and the nutritional status of stranded whales.

Although Indo-Pacific bottlenose dolphins (Tursiops aduncus) are a valued component of the Swan-Canning Estuary and the Swan Canning Riverpark, little is known about the health and ecology of the small community of dolphins inhabiting the estuary. To improve the scientific basis for management, we examined the population genetics, trophic associations, and contaminant exposure of dolphins within the estuary. This Swan Canning Research Innovation Program (SCRIP) study had the following objectives: (1) detail contaminant concentrations in dolphins (as a baseline for future monitoring); (2) provide a preliminary assessment of health risk posed by contaminants to dolphins; (3) examine trophic pathway associations for Swan River bottlenose dolphin community; (4) use genetic information to examine whether bottlenose dolphins from the Swan-Canning Estuary and adjacent waters (Cockburn Sound) represent one homogenous population or (alternatively) if fine-scale population structuring occurs; and (5) put project findings into the perspective of system ecology and management implications. Tissue samples for this study were obtained through remote biopsy sampling of free-ranging dolphins and the collection of tissues during post-mortem examinations under permits and licences from the WA Department of Environment and Conservation and the Murdoch University Animal Ethics Committee.

This technical report reviews findings from an investigation into the mortalities of six bottlenose dolphins (Tursiops aduncus) in the Swan Canning Riverpark in 2009. The report: (a) describes the epidemiology and pathology of these mortalities; (b) presents background information on the ecology of dolphins in the Swan Canning Riverpark and factors known to affect dolphin health; and (c) discusses the potential role of chemical contaminants in the mortalities. These mortalities were investigated in context of dolphin deaths in the Swan Canning Riverpark prior to 2009 and a series of mortalities of dolphins in the Bunbury area between 2008-10, as well as marine mammal mortality events in other locations.