Cetaceans of the Northern Bismarck Sea, Papua New Guinea1

Abstract: There is little known about cetaceans in the waters of Papua New Guinea (PNG). Here we present findings from the first two sets of cetacean sighting and acoustic surveys conducted within the Admiralty Island group in the northern Bismarck Sea. More than 1,000 cetaceans were sighted during our boat-based surveys–the most common being spinner dolphins (Stenella longirostris), followed by pantropical spotted dolphins (Stenella attenuata), short-finned pilot whales (Globicephala macrorhynchus), and sperm whales (Physeter macrocephalus). The relative group size of spinner dolphins was different between years with group sizes in 2010 being significantly lower (median = 15, range = 2–50) than those recorded in 2013 (median = 50, range = 5–100). The presence of large aggregations of spinner dolphins (including calves) as well as sightings of Vulnerable sperm whales suggest the northern Bismarck Sea as an area of conservation importance for cetaceans. Our surveys also provide useful baseline data for a variety of marine protected area planning processes and management initiatives that are ongoing in PNG.