Confirmed occurrence of the Australian snubfin dolphin (Orcaella heinsohni) in Papua New Guinea: conservation considerations for small isolated populations

Context The taxonomic status of Orcaella spp. in Papua New Guinea waters is unknown. The Australian snubfin dolphin (Orcaella heinsohni) has been identified from northern Australian waters south of Papua New Guinea, and the Irrawaddy dolphin (Orcaella brevirostris) from Borneo north-west of Papua New Guinea. Aims This study analysed samples of Orcaella spp. from Papua New Guinea and northern Australia to confirm the species of Orcaella that occurs in Papua New Guinea waters. Methods Genetic analyses were conducted on 11 Orcaella spp. samples from Papua New Guinea and eight new Australian snubfin dolphin samples from northern Australia, including the type specimen. A 489-base sequence of the mitochondrial control region (HVR-1) was analysed using Maximum Likelihood and Bayesian Inference to infer phylogenetic relationships. Key results Phylogenetic reconstruction showed that the Papua New Guinea samples are nested within Australian snubfin dolphin samples and did not form a monophyletic group. Conclusions These results confirm that the Australian snubfin dolphin occurs in southern Papua New Guinea. Implications There are no confirmed records of Orcaella spp. from other regions of Papua New Guinea, or the Pacific Islands. The geographic demarcation between Australian snubfin and Irrawaddy dolphin populations remains unknown, although it is located within the Wallacea region. The viability of this apparently small, isolated population of Australian snubfin dolphins is uncertain. The main threat to this population is accidental by-catch in gillnet fisheries. Conservation and management strategies that focus on mitigating by-catch are urgently required.