Passive acoustic monitoring of Antarctic marine mammals

Brief description

Metadata record for data from ASAC Project 2683. This project was followed by AAS project 4102, "Population abundance, trend, structure and distribution of the endangered Antarctic blue whale". The metadata record for project 4102 (and its child records) is available at the provided URL.

This metadata record is in the process of being gradually modified (2014-08-08) to be set up as a parent record for the data from the above listed projects. Data from these projects will gradually become available via child records, rather than this record.

Public Summary - 2683
This project will initiate focused acoustic research into the biology of Southern Ocean cetaceans. Deployment of sonobuoys along vessel transects will be used to survey large geographic regions for the presence and relative abundance of cetaceans. In addition, bottom mounted acoustic recording devices will permit continuous acoustic monitoring of targeted locations over long time frames. These techniques will help answer important questions regarding the presence, relative abundance, seasonality, movements, and distribution of Southern Ocean marine mammals that are necessary for effective management.

Public Summary - 4102
Half a century ago the Antarctic blue whale was perilously close to extinction. Over 350,000 were killed before the remaining few were fully protected. A decade ago this elusive and poorly understood species was estimated to be less than 5% of its pre-whaling abundance. This multi-national, circumpolar project will develop and apply powerful new techniques to survey these rare whales and gain an insight into their recovery and ecology. The project is the flagship of the Southern Ocean Research Partnership - an International Whaling Commission endorsed collaborative program.

Project objectives:
This multi-year initiative within the AMLR program aims to implement a focused acoustic research program that will examine Southern Ocean marine mammal population dynamics through the use of technologically advanced acoustic monitoring techniques. In order to achieve the aims of this study an international collaboration has been developed leading to a multi-faceted research program. Long-term autonomous sea-floor recording devices will be utilised to conduct year-round acoustic surveys in targeted locations. Sonobuoys will additionally be used over shorter time frames to conduct strategic vessel-based acoustic surveys over large geographic ranges. These data will be used to assess distribution, movement, relative abundance, seasonality, and behaviour of cetaceans in Southern Ocean waters. These results can then be integrated with concurrently collected data on oceanographic and biological variables from vessel based surveys and remote satellite sensing leading to a larger understanding of the role of marine mammals in the Southern Ocean ecosystem.

These objectives and early research design of this project are largely responsive to needs determined by the Australian Antarctic Division's recently inherited responsibilities to the International Whaling Commission. The prevailing motivation behind this project is to help develop a significant acoustic research capability in cetacean biology in order to provide sound scientific data that will assist in Australia's participation in the International Whaling Commission.

Data from this project are stored offline on servers held at the Australian Antarctic Data Centre.

Taken from the 2008-2009 Progress Report:
Progress against objectives:
Analysis of the Brokewest sonobuoy survey is complete and the manuscript has been accepted for publication in Deep Sea Research. This manuscript details the distribution of whales and seals in eastern Antarctic waters based on an acoustic sonobuoy survey. Data analysis is continuing of the recovered acoustic logger data. In addition, 1 acoustic logger was recovered during the 2008/9 season that will provide 2 years of acoustic recordings from the waters between Tasmania and the Antarctic. Unfortunately, 2 other loggers deployed last year were unable to be recovered and appear to be lost. Finally, 2 years of low frequency hydro-acoustic data from the northern Indian ocean (Diego Garcia) has been obtained from the CTBTO. This will permit comparisons with the Southern Ocean data to assess differences in seasonality and presence of calling whales

Taken from the 2009-2010 Progress Report:
Progress against objectives:
In the last year, we have made significant progress on three fronts. First, we conducted a sonobuoy survey as part of the Antarctic Whale Expedition (AWE) which took place in February-March 2010. One hundred eleven sonobuoys were deployed across the study area (south of 60 degrees latitude, and between 150W and 150E longitude). Blue, fin, minke, humpback, sperm, killer, and unidentified beaked whales were all recorded. Two significant findings include linking the minke whale to a song-like vocalization that may be used to acoustically monitor these populations, and recording humpback whale song on the Southern Ocean feeding grounds for the first time. In addition, a long-term acoustic logger was deployed on the seafloor off Casey station for recovery in the 2010/2011 season, and a long term recorder deployed off the Kerguelen Plateau in collaboration with the French was recovered and is currently in transit back to Australia. And finally, we've begun redesigning the acoustic logger moorings for more efficient future deployments.

Lineage

Progress Code: completed

Statement: The Dates provided in temporal coverage are approximate only, and represent the beginning and end of the 2005 - 2012 Antarctic seasons.

The latitudes and longitudes provided in spatial coverage are approximate only.

The following information relates specifically to the Tangaroa.Sonobuoy.Log.xls file:

National Instruments Card Gain is the amount of gain the sound card added to the signal.

1 gain means the input voltage range is from -5 to +5 volts
5 gain means the input voltage range is from -1 to +1 volts I think we ended up using a gain of 5 in most cases since even loud audio signals were typically between +/-1 V.

Basically, these set the bounds/rails on what the sound card can read as part of an acoustic signal. If the signal is particularly intense and produces a higher voltage than +/-1 (in the case of a gain of 5) then the signal peaks or 'hits the rail' and is still recorded as a +/-1V signal (distorting the sound recorded). The voltage range of the audio signal is determined by a chain of things from the hydrophone sensitivity on the sonobuoy and how this is transmitted to the boat's receiver, and ultimately the sensitivity of the VHF receiver in converting the VHF signal back to an audio signal. Check the dataset for calibration files.

The manual for the sound card can be found at the following website:
http://www.ni.com/pdf/manuals/370503k.pdf

2. Unit for frequency should be Hz (hertz).
3. Depth is Meters
4. Yellow highlighted boxes are from sonobuoys that failed (i.e. they were deployed, but no or minimal useful audio signal was recorded from them)

Taken from the 2008-2009 Progress Report:
Field work:
As described above, recovery attempts were made on 3 acoustic dataloggers that were deployed in 2007/8 along a line of longitude south of Tasmania (142 E) from just SW of Tasmania (44 S), to halfway between Tasmania and the Antarctic (54 S), to just off the Antarctic continental shelf (65 S). These instruments will be recovered during the 08/09 season. Unfortunately, 2 of the loggers did not respond to acoustic communication or release attempts and are considered lost. The remaining instrument will need to be supplemented with additional acoustic recorders to be deployed during the 2009/10 season

Laboratory activity/analysis:
Analysis of the BrokeWest dataset was completed and a manuscript was accepted for publication. Analyses of the acoustic data from the long-term loggers has continued. These analyses identified the relative seasonal presence of calling whales by measuring the energy at signature frequency bands for blue (both pygmy and Antarctic) and fin whales. Over the next year, including the new datasets obtained, these analyses should be completed and be ready for writing up for publication.

Difficulties affecting project:
Two acoustic loggers were lost this season. Up until now, we have had a perfect recovery rate. At some point, loss of a logger or two was inevitable considering the extreme conditions they are being deployed in (2-3000m depth in the Southern Ocean for year long periods). However, since these instruments will need to be replaced, it will be a good time to look at their design and determine if improvements can be made.

Taken from the 2009-2010 Progress Report:
Field work:
As described above, an acoustic sonobuoy survey took place on the AWE whale research voyage between 150W and 150E longitude, and primarily below 60S latitude. Approximately 150 hours were recorded and analysis of these data is ongoing. A long term acoustic recorder deployed off the Kerguelen Plateau in collaboration with the French was recovered and is currently in transit back to Australia. In addition, a seafloor mounted acoustic logger was deployed off Casey station. This instrument will be recovered in the 2010/11 season and will have recorded underwater sound for the previous year.

Laboratory activity/analysis:
Analyses of the acoustic data from recent AWE sonobuoy survey has just begun, and analyses of the long-term loggers has continued. These analyses have identified the relative seasonal presence of calling whales by measuring the energy at signature frequency bands for blue (both pygmy and Antarctic) and fin whales. A new dataset totalling 6 years of acoustic data off the west coast of Australia, and 3 years from the northern Indian Ocean were obtained and analysed. This will allow comparisons with concurrent recordings from Southern Ocean waters. With these new datasets obtained, these analyses should be completed and be ready for writing up for publication in the next few months.