Your access to IMOS Acoustic Observatory data discovery and exploration is through the Australian Ocean Data Network (AODN) Portal.
A summary of all IMOS passive acoustic data collected with one representative instrument for each deployment-period/site highlighted is given here. The set number is a number allocated by Curtin for that deployment and is not necessarily in order by time or location. Note that temperature data is available from each site for each deployment, contact IMOS for these data.
Note in many deployments multiple loggers were set per deployment and for tracking grids each logger had two sample schedules, the normal 15 minute 6 kHz samples and a shorter 20 or 22 kHz sample once per day. The instances where multiple loggers were used per deployment have been for tracking purposes, the loggers were set in a grid of four, 1) to the SE, 2) to the SW, 3) to the north in an equilateral triangle of approximately 5 km sides, and 4) in the triangle centre. An acoustic release on the centre mooring was set to ping over 35 minutes every 20 s at 7.5 kHz. These pings were captured by the 22 kHz samples (also by the 6 kHz samples) and used to synchronise the instrument clocks (set three clocks relative to a fourth). Analysis of these data sets is complex, especially for synchronising the clocks, so users are asked to contact Rob McCauley (email below) if they wish to pursue tracking analysis. See Gavrilov, A.N., McCauley R.D., Pattiaratchi C., Bondarenko, O. (2012) The use of passive acoustics to observe the presence and movement of pygmy blue whales (Balaenoptera musculus brevicauda) in the Perth Canyon, WA. Proceedings of the 11th European Conference on Underwater Acoustics, July 2012 Edinburgh, UK. Proceedings Institute Acoustics 34(3) for an example of the tracking capability.
The data can be used for various purposes including (but certainly not limited to):
- studies of vessel traffic - Passing vessels produce distinctive noise signatures, these can be related to vessel movements;
- recording man made noise such as vessel or marine seismic noise - Moored sea noise loggers can give long term statistics on the amounts of noise produced by various man made activities, with two of the more common noise sources being ships and offshore marine seismic surveys;
- studies into ambient noise - Wind, rain, ice related noise, earthquakes even swell and sea state are some examples of relatively common natural sources which greatly influence ambient noise levels. The ambient noise statistics can be used in turn, to define the physical factors raising sea noise, such as wind speed or rainfall frequency and intensity.
- studies into fish presence - Fish can call independently, commonly en-masse in large schools, or somewhere in between, often regularly raising ambient noise levels in the frequency band of their calling by significant amounts. By knowing the characteristics of a fish species call type (they generally have only a limited repertoire) and having some knowledge of why and how they are producing the call, then one can obtain long term information on trends and behaviour for different fish species. Since a sea noise logger is integrating information over a large area, approximately one km for an individual fish call or perhaps 10-50 km for fish choruses as detected by the IMOS observatories, then the sea noise offers a long term, large scale technique for monitoring.
- studies into whale habits, migrations and seasonal presence - Most baleen whale species produce vocalisations which may be detected at many tens of km. The IMOS sea noise loggers are optimised to detect these signal types. The sea noise data allows yearly monitoring of these whales, for example allowing us to define which species will travel up and down our coasts, when they may go past and with work, how many pass each year. This technique is the only reliable way to monitor our offshore great whales, which the IMOS sea noise loggers have shown are common and involve a multitude of species from all the primary sites.
One of the great powers of the sea noise logger sampling is the high time definition available over long time frames. This allows the data to be used to study natural rhythms in calling animals at a resolution which is simply not available to any other technique in the ocean. Marine animals do not have watches and have never heard of the Julian calendar, the precursor to our current Gregorian calendar. Their rhythms are based on day length, moon phase and summer and winter solstices in complex ways that the sea noise logger data is beginning to elucidate. An example of the seasonal nature of fish calling is presented in: McCauley RD., (2012) Fish choruses from the Kimberley, seasonal and lunar links as determined by long term sea noise monitoring. Australian Acoustical Society Proceedings of Acoustics 2012 - Fremantle 6pp.
As an example of what the IMOS sea noise loggers can tell us in the long term, consider pygmy blue whales in the Perth Canyon. We have been monitoring these whales with IMOS gear since 2008 and in total since 2000. We can now reliably predict the seasonal visitation of these whales each year, using data from previous years adjusted for the whale's seasonal clock which is not based on our Gregorian calendar, then displayed on our Gregorian calendar. For example the figure below shows the predicted pygmy blue whale visitation for 2016. The pygmy blue whales arrive in the Perth Canyon on their northbound migratory leg, will stay if there is food present, then depart. Using each of these stages: 1) arrive; 2) period when they may stay to feed; and 3) migratory tail, and the corrected seasonal time base, we can look at the trend across time of the population based on numbers of whales calling. This is also shown as a figure below.