Abstract
This study assessed the status of Indo-Pacific bottlenose dolphins (Tursiops aduncus) within the Swan Canning Riverpark (SCR), Perth, Western Australia following the death of six dolphins in 2009. Between June 2011 and February 2013, 29 dolphins (excluding calves) were photo-identified during boat-based surveys (n = 76 days). Analyses of sighting rates, Lagged Identification Rates (LIR), and association patterns (Simple Ratio Index, preferred dyadic association analyses, and Lagged Association Rates (LAR)) yielded an estimated ‘community size’ of 16-18 individuals (excluding calves), similar to the estimated 17-18 residents present in 2001-3. Only 9 dolphins identified in 2001-3 were still present. LARs for adult males and adult females were best explained by a constant companion association model and a long-lasting association model, respectively. Six females (including 3 with dependent calf) were mainly observed in coastal waters adjacent to the SCR. The model best-fitting the LIRs indicated a pattern of emigration and reimmigration in which individuals were not sighted in the SCR for a period of 12-17 days. Thus, dolphins considered resident within the SCR also range within adjacent coastal waters and interact with other dolphins there. Several females with calf were consistently observed in the SCR in late summer, suggesting the estuary provides particular benefits to nursing females at that time. Future studies should investigate the genetic and demographic connectivity of the community to other dolphin populations and the appropriateness of the resident community as a management unit for the SCR.