Fisheries Acoustics Transects
Remote sensing of the aquatic environment is an invaluable tool for observing the processes that occur over wide spatial and temporal scales. In water, sound energy propagates readily and the reflected energy can be used to investigate what lies beneath the surface. Using the sound to investigate the behaviour, abundance and distribution of biological organisms is known as Fisheries Acoustics. While much of focus in Fisheries Acoustics is on fish, the technique is also applied to much smaller and larger organisms such as plankton and marine mammals.
The web mapping tool for this project allows users to see where NIWA has undertaken fisheries acoustic surveys, and, by clicking on the transect on the map, view information about the acoustic transect and a preview of the echogram. A full A4 sized image can be downloaded if required. Note that retrieving and rendering the 16,000 transects on the map page may take several seconds. For a faster response, you can just view a subset of recent transects instead of all of them, by chosing the layers to be displayed from the layer menu.
NIWA has collected Fisheries Acoustics data over much of the New Zealand's EEZ, and sometimes further afield, for the last 20+ years down to depths of over 1500m. These data are collected from research and commercial vessels using sophisticated echosounder systems which broadcast sound energy into the water and record, process and analyse the reflected sound. Much of the data have been collected as part of Government-funded projects (primarily New Zealand's Ministry for Primary Industries (MPI) for stock assessments) and are able to be made publicly available through open source licences. Some of the data which are not currently provided online relate to:
- Equipment calibration and testing,
- Data collected for commercial clients,
- Data collected from Antarctic toothfish vessels,
- Multi-frequency data
Some transects were taken for core survey purposes, such as to determine acoustic biomass of the target species, others were opportunistic, captured during steams between survey sites. All data which are able to be made publically available are displayed on the map.
One way of visualising Fisheries Acoustic data is with an 'echogram' like the one above, which is a picture showing the reflected sound (echos) from the sea bed, fish schools and other objects in the water column.