2012 Blue whale voyages in the Bonney Upwelling, Australia

Brief description

This metadata record is a parent for all data collected during the 2012 Blue whale voyages. Description of specific data sets can be found within child datasets.

Lineage

Progress Code: completed

Notes

Purpose
The Antarctic Blue Whale Project (ABWP; an initiative within the International Whaling Commission Southern Ocean Research Partnership - IWC SORP) has the primary aim of estimating circumpolar abundance of Antarctic blue whales (Balaenoptera musculus intermedia). Mark-recapture methods, using genetics and photo-ID, will form the foundation of future blue whale circumpolar abundance estimates produced by the ABWP, but the success of these methods require a high number of encounters with these animals. In the Southern Ocean, acoustic detection ranges of blue whales far outstrip visual sighting ranges, so real-time acoustic tracking can be used to increase the total number of whale sightings, thus making more efficient use of expensive ship time. Before undertaking an Antarctic blue whale research program that features acoustic tracking, instrumentation and methods specific to acoustic tracking of blue whales must be developed, and the capabilities and limitations of such an acoustic tracking system should be quantified. The Australian Antarctic Division undertook two voyages, both three weeks in length, in January and March, 2012, respectively. The surveys targeted the Bonney Upwelling, along the south-east coast of Australia, an area known to be a summer (Nov-May) feeding ground for pygmy blue whales; the surveys focussed on the area bounded by 141.0-143.0 degrees E and 38.0-39.5 degrees S. These voyages were undertaken in order to address the practicalities of 24-hour/day real-time acoustic tracking. Achieving these goals required characterising the capabilities of the acoustic tracking system, assessing the practicality and performance of different survey protocols, and integrating acoustic tracking with visual survey methods and mark-recapture methodologies. Of the six weeks allocated across both surveys, weather allowed for a total of 20 survey days (ten for each survey). The tracking system operated continuously during the voyages recording nearly 500 hours of audio, while acousticians processed over 7000 blue whale calls all in 'real-time'. During the voyages 33 vocalising blue whales were pursued via acoustic tracking and of these 28 yielded visual sightings of groups of one or more whales, giving a combined acoustic success rate of 85%. Sighting effort was 785 n.miles during the January voyage and 669.6 n.miles during March voyage, over 127.0 and 104.7 hours, respectively. The first voyage yielded 37 sightings of blue or like blue whales; a total of 70 animals. During the second voyage there were 15 sightings of blue or like blue whales; 34 animals in total, in addition to three sightings of unidentified large baleen whales. Other noteworthy sightings include groups of Shepherd’s beaked whales (Tasmacetus shepherdi) on both surveys; a sei whale in the first survey; and a fin whale in the second survey. Photo-ID during the first voyage identified 24 individuals; there were 24 individuals identified during the second voyage as well. There was one animal re-sighted between the two voyages, leaving 47 individuals identified in total.