Population genetic structure of the Burrunan dolphin (Tursiops australis) in coastal waters of south-eastern Australia: conservation implications

Deep Sea Research Part II: Topical Studies in Oceanography

2018

This study provides the first assessment of the occurrence, distribution and abundance of cetaceans in shelf and coastal waters off the western Eyre Peninsula, eastern Great Australian Bight, South Australia. We undertook aerial line-transect surveys to estimate the abundance of common dolphins, and to assess the occurrence and distribution of other small and large 2 cetaceans. Two along shore surveys were also flown to assess occurrence of endangered southern right whales in coastal waters. Five cetacean species were detected: seven southern right whales, three humpback whales, one minke whale (unknown species), 71 schools of shortbeaked common dolphins, and 14 schools of bottlenose dolphins. Abundance of common dolphins was estimated to be 20,000-22,000 using distance sampling methods with densities of 0.67-0.73 dolphin/km 2. Comparisons or shot-beaked common dolphin densities off the Eyre Peninsula in the eastern GAB with other regions around the world show that shelf waters off the Eyre Peninsula represent an important habitat for common dolphins.

Section: Discussionmentioning

confidence: 99%

Section: Line-transect Surveymentioning

confidence: 90%

Occurrence, distribution and abundance of cetaceans off the western Eyre Peninsula in the Great Australian Bight

Bilgmann

Parra

Deep Sea Research Part II: Topical Studies in Oceanography

2018

“…australis; Figure 1). Only two small resident populations of southern Australian bottlenose dolphins are known to occur in Victoria (Charlton-Robb, Taylor, & McKechnie, 2015), while recent studies indicate that this species is relatively abundant in South Australia (Passadore, Möller, Diaz-Aguirre, & Parra, 2017;Zanardo et al, 2016). Capture-recapture modeling of photographicidentification (photo-ID) data and molecular analyses of biopsy samples collected in the inner area of Coffin Bay, an inverse estuary located in temperate waters of a multiple-use marine park in South Australia, indicated that this area offers highly favorable habitat for both males and females of this species (Passadore et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

High site fidelity and restricted ranging patterns in southern Australian bottlenose dolphins

Passadore

Diaz‐Aguirre

et al. 2017

Ecology and Evolution

Information on site fidelity and ranging patterns of wild animals is critical to understand how they use their environment and guide conservation and management strategies. Delphinids show a wide variety of site fidelity and ranging patterns. Between September 2013 and October 2015, we used boat‐based surveys, photographic identification, biopsy sampling, clustering analysis, and geographic information systems to determine the site‐fidelity patterns and representative ranges of southern Australian bottlenose dolphins (Tursiops cf. australis) inhabiting the inner area of Coffin Bay, a highly productive inverse estuary located within Thorny Passage Marine Park, South Australia. Agglomerative hierarchical clustering (AHC) of individuals’ site‐fidelity index and sighting rates indicated that the majority of dolphins within the inner area of Coffin Bay are “regular residents” (n = 125), followed by “occasional residents” (n = 28), and “occasional visitors” (n = 26). The low standard distance deviation indicated that resident dolphins remained close to their main center of use (range = 0.7–4.7 km, X ± SD = 2.3 ± 0.9 km). Representative ranges of resident dolphins were small (range = 3.9–33.5 km2, X ± SD = 15.2 ± 6.8 km2), with no significant differences between males and females (Kruskal–Wallis, χ2 = 0.426, p = .808). The representative range of 56% of the resident dolphins was restricted to a particular bay within the study area. The strong site fidelity and restricted ranging patterns among individuals could be linked to the high population density of this species in the inner area of Coffin Bay, coupled with differences in social structure and feeding habits. Our results emphasize the importance of productive habitats as a major factor driving site fidelity and restricted movement patterns in highly mobile marine mammals and the high conservation value of the inner area of Coffin Bay for southern Australian bottlenose dolphins.

“…In Victoria, two inshore populations of southern Australian bottlenose dolphins have been studied, one in Port Phillip Bay (~80-120 individuals) and another in Gippsland Lakes (~50-150 individuals) (Charlton-Robb et al, 2011;Charlton-Robb, Taylor, & McKechnie, 2015;Dunn, Goldsworthy, Glencross, & Charlton-Robb, 2001;Filby, Stockin, & Scarpaci, 2014;Scarpaci, Dayanthi, & Corkeron, 2003). The species is listed as threatened under the 'Victorian Flora and Fauna Guarantee Act 1988' because of their small and resident population status (Dunn et al, 2001), as well as genetic distinctiveness (Charlton-Robb et al, 2011).…”

mentioning

confidence: 99%

Demography of southern Australian bottlenose dolphins living in a protected inverse estuary

Passadore

Diaz‐Aguirre

et al. 2017

Aquatic Conservation

Assessments of demographic parameters are essential to understand the dynamics of wild populations, and for their efficient conservation and management. Here, sex‐specific abundance, apparent survival and temporary emigration of southern Australian bottlenose dolphins (Tursiops cf. australis) in Coffin Bay (CB), South Australia, is investigated. Results are based on capture–recapture modelling of photo‐identification data and molecular analyses of biopsy samples collected during boat‐based surveys between September 2013 and October 2015 in the inner and outer areas of CB. The total super‐population of dolphins (including calves) using the entire study area (263 km2) was estimated with POPAN models at 306 (95% CI: 291–323), which included 71 (68–73) marked females and 57 (55–60) marked males. Seasonal estimates of abundance for the inner area of CB (123 km2) obtained with Pollock's Closed Robust Design models remained relatively constant over the two years (marked females: 52–60, marked males: 46–52, and total: 193–209). The high density of dolphins inhabiting the inner area (seasonal range: 1.57–1.70 individuals km−2), high apparent survival rates estimated for both sexes (females: 0.99; 95% CI: 0.96–1.0; males: 0.95; 0.82–0.99), and low temporary emigration rates (0.02; 95% CI: 0.01–0.11) indicate that the inner area of CB offers highly favourable habitat for these dolphins. 6‐High biological productivity and low predation risk may promote these demographic patterns in the inner area of CB. 7‐This study provides a robust baseline of sex‐specific population demographics of southern Australian bottlenose dolphins with important implications for future research and their management and conservation in South Australia.