For many marine organisms, including large, long-lived predators, the factors affecting connectivity between populations are still largely unknown. We assessed levels of genetic differentiation and dispersal patterns of bottlenose dolphins Tursiops sp. across Spencer Gulf and coastal areas west of the gulf in the Great Australian Bight, South Australia (SA), using data from mitochondrial DNA control region sequences and 6 microsatellite loci. Marked genetic differentiation and low migration were detected between dolphins of Spencer Gulf and those inhabiting coastal areas west of the gulf. We hypothesise that the restriction to dolphin gene flow is influenced by an oceanographic front at the mouth of Spencer Gulf that builds up over the austral summer and exhibits strong differences in water temperatures and salinity levels. It appears that the genetic subdivision reported here is a recent phenomenon, a finding consistent with the known geomorphologic history of the region. Coastal bottlenose dolphins from SA are evolutionarily divergent from other bottlenose dolphin species and are potentially under threat due to ongoing human-related mortality. The information from this study can, therefore, be used for the development of much-needed conservation management strategies.

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Huveneers, C., Otway, N. M., Gibbs, S. E., and Harcourt, R. G. 2007. Quantitative diet assessment of wobbegong sharks (genus Orectolobus) in New South Wales, Australia. – ICES Journal of Marine Science, 64: 1272–1281. The diets of three species of wobbegong (Orectolobus ornatus, O. maculatus, and O. halei) in New South Wales, Australia, were investigated using stomach contents from specimens caught by commercial fishers. Some 80% of wobbegongs caught by commercial setline, and 60% caught by trap or scuba diving, had empty stomachs, most likely due to regurgitation. Wobbegongs were frequently hooked in the stomach (80–90% of the catch), potentially contributing to the greater proportion of empty stomachs compared with other species of shark. The diet of all three species was primarily osteichthyans, but with some cephalopods and chondrichthyans. Interspecific differences in the diets were related to total length of the shark. Octopuses were more frequent in the diet of O. ornatus (dwarf ornate wobbegong) than other wobbegong species, possibly through the smaller adult size facilitating capture of octopuses in small holes/crevices. Orectolobus halei fed more frequently on pelagic species and chondrichthyans, possibly because of their greater mobility. Wobbegongs feed at a high trophic level, and their removal from their ecosystem may impact lower trophic levels.

Context Animal species with overlapping ranges are common worldwide, but how these species coexist is less obvious. Dolphins are protected in Australia and yet little information is available on their resource use which is essential for successful management and conservation. Aim The aim of this study was to determine the degree of overlap in diet and feeding ecology of the two Tursiops spp. that have overlapping ranges in South Australia. Methods Stomach content (91 Tursiops sp. and 14 T. truncatus) and stable isotope (δ13C, δ15N) analyses (39 Tursiops sp. and 14 T. truncatus) were conducted. Carcasses of dolphins were opportunistically collected between 1974 and 2005. Diet was quantified by frequency of occurrence (FOO) and numerical abundance (NA) of prey. Key results Delta13C from teeth revealed distinct differences in primary source of carbon, corresponding to coastal (Tursiops sp. n = 39,  = –12.24, s.d. = 1.32) and offshore habitats (T. truncatus n = 14,  = –14.21, s.d. = 0.55). Differences in δ15N revealed Tursiops sp. ( = 11.66, s.d. = 0.58) feeds at a lower trophic level than T. truncatus ( = 14.29, s.d. = 0.88). Stomach content analyses for Tursiops sp. corroborated stable isotope results. There was a significant difference between the diets of Tursiops sp. from north Spencer Gulf and south Spencer Gulf (ANOSIM R = 0.249, P = 0.001). Prey were generally demersal in habit with the most important from the cephalopod families Octopodidae, Sepiidae and Loliginidae and fish families Carangidae, Clupeidae, Terapontidae and Apogonidae. For T. truncatus there were insufficient stomach contents for assessment. Conclusions South Australian bottlenose dolphin species exhibit distinct niche differentiation with clear evidence of regional variation in the diet of Tursiops sp. Implications The between and within species diet differentiation demonstrated, highlights the importance of regional management. Such results are internationally significant as coastal and offshore forms of Tursiops spp. occur worldwide.