Offshore industry and whales: Pygmy blue whale acoustic behavior and movement patterns in the Otway Basin

Abstract

The offshore Otway region of Australia is designated as a Biologically Important Area for foraging for blue whales. Understanding the acoustic behavior of blue whales in these foraging grounds will enable an improved understanding of the residency time of individual animals and facilitate improved management of the population. JASCO deployed a directional AMAR G4 for part of the 2020 pygmy blue whale foraging season. The recorded vocalizations, including song and D-calls, have been analyzed in detail to determine bearings, received level, and estimated ranges. Bearings to detected vocalizations were determined using a maximum-likelihood-estimator, with a fluid only propagation model corrected for the layered elastic seafloor used to determine ranges. An analysis of the distribution of different vocalizations across the listening range of the AMAR over time has been conducted and correlated with AIS information from shipping traffic. The results have been used to provide a brief insight into the acoustic behavior and movement patterns of individual pygmy blue whales within the region, furthering our understanding of spatial habitat use in association with commercial shipping lanes and oil and gas operations.