UNDERWATER ACOUSTICS

Southern right whales produce distinct call types for communication. Passive acoustic monitoring of southern right whale calls offers the capability to increase our understanding of the social interactions, offshore distribution, migration times and movement of whales between known aggregation areas. Underwater noise recordings collected at Fowlers Bay and Head of Bight (in collaboration with Curtin University and Fowlers Bay Eco Whale Tours) will be used to characterise the vocalisations of southern right whales. Call types will be correlated with behaviour (swimming, resting, mating, surface active, etc.) and classification (cow-calf pair, unaccompanied adult, juvenile) to determine whether a relationship exists. The presence/absence of southern right calls on underwater noise recorders will indicate their movement, and provide a density estimate of whales in the area.

Passive acoustic monitoring provides an alternative to visual monitoring. It is particularly useful in offshore areas or areas of unfavourable environmental conditions as it can be used at night and in poor weather conditions. It can detect vocalising animals in all directions over much longer ranges, and often detects higher numbers of animals than visual observations alone.

Underwater acoustic methods used in the Great Australian Bight to study southern right whale vocalisations and other biological noise include an autonomous moored underwater noise recorder located offshore from the aggregation grounds, a temporarily moored sound trap (small autonomous noise recorder), and a handheld hydrophone deployed from a vessel. Recordings can last up to 6 months each deployment.

The GABWRS team aims to use underwater acoustics to address objectives in the Commonwealth Conservation Management Plan for the Southern Right Whale 2011-2021, to better understand their offshore distribution and movement patterns.