Sperm whales in the Great Australian Bight: Synthesising historical and contemporary data to predict potential distribution

Abstract

Sperm whales have been identified under Marine Bioregional Plans as key features in the Great Australian Bight (GAB). Although commercial whaling of sperm whales in Australian waters ceased in 1978 there is no evidence of recovery of sperm whale populations. Information on the current distribution and abundance of sperm whales in the region, which is also an important area for human activities including fishing, oil and gas exploration and tourism, is very limited. We undertook a systematic visual and passive acoustic vessel based survey in the central eastern GAB. The visual detection rate of sperm whales from the survey was 1.4 individuals per 1000 km with an acoustic density of 0.21 individuals per 1000 km2. We combined these sightings and detection data with historical and contemporary whaling and sightings data to identify critical habitat for sperm whales in the region. Using Maximum entropy modelling, suitable sperm whale habitat was predicted over the continental shelf break, but more specifically, over sub-marine canyons. Baseline information on the abundance and distribution of sperm whales, and other cetacean species, in the GAB are required to provide information to management agencies and regulators in order to assess and mitigate risks. The potential impacts of increased noise from shipping, seismic surveys and construction on cetacean species in the region need to be considered.