Observations on Australian Humpback Dolphins (Sousa sahulensis) in Waters of the Pacific Islands and New Guinea

Abstract

The Australian humpback dolphin, Sousa sahulensis, has recently been described to occur in northern Australian coastal waters. However, its distribution in adjacent waters of the Pacific Islands and New Guinea remains largely unknown. Although there have been few studies conducted on inshore dolphins in these regions, the available information records humpback dolphins primarily from the Kikori Delta in Papua New Guinea, and Bird's Head Seascape in West Papua. Research in southern Papua New Guinea indicates that humpback dolphins are indeed S. sahulensis, based on cranial and external morphometrics, external colouration and the preliminary genetic analysis presented here. A similar situation exists for the Australian snubfin dolphin, Orcaella heinsohni, where it is assumed that the species also occurs along the Sahul Shelf coastal waters of northern Australia and New Guinea. There are anecdotal reports of direct catch of Australian humpback dolphins for use as shark bait, coastal development is increasing, and anthropogenic impacts will continue to escalate as human populations expand into previously uninhabited regions. Future research and management priorities for the Governments of the Pacific Islands and Indonesia will need to focus on inshore dolphins in known regional hotspots, as current bycatch levels appear unsustainable.

Keywords: Australian humpback dolphin; Pacific Islands; Papua New Guinea; Sahul Shelf; Sousa sahulensis; West Papua.