In addition to monitoring pelagic fish and sharks using baited video cameras, University of Western Australia and Marine Hub PhD candidate Phil Bouchet and postdoctoral fellow Dr Tom Letessier have been collecting valuable observation data on the occurrence and distribution of seabirds and surface air-breathers such as sea snakes, turtles and marine mammals. So far, over 100 sightings have been made in over 16 hours of effort, both within and outside our focal sampling areas. Bird assemblages have been particularly diverse, with a minimum of seven confirmed species groups (including boobies, terns, petrels, shearwaters, plovers, frigatebirds and storm petrels), which is indicative that the Timor Sea is home to a large range of wildlife.

Among the highlights are several encounters with charismatic cetaceans, including a mixed species aggregation of Indo-Pacific bottlenose dolphins (Tursiops aduncus) and false killer whales (Pseudorca crassidens) in our first focal sampling area (19/09/2012), and a pod of three killer whales (Orcinus orca) in our second focal sampling area (22/09/2012). Deck operations were temporarily halted to allow for positional data and photographs to be taken. Our observations showed that these animals engaged in socialising, resting and feeding behaviours – in particular, the false killer whales were observed circling an injured sailfish and the killer whales were followed in an area where large schools of mackerel were also captured on video. All groups comprised one or more calves and juveniles, supporting the idea that this part of the Timor Sea might be critical to several of the toothed cetacean species at various stages of their life cycles.

As we prepare to steam back to Darwin to refuel before sampling the third and last focal area, additional observations will be collected which will contribute to building a more complete picture of marine predator distributions near the Australian northern frontier.

Phil Bouchet
University of Western Australia

Image 1 - Bottlenose dolphin on the bow (Photo: Tom Letessier)

Image 2 - False killer whale diving (Photo: Phil Bouchet)

Image 3 - Killer whale calf riding waves with adults beneath the surface (Photo: Phil Bouchet)

Image credits:  Phil Bouchet, UWA