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Swath Sonar System Mapping Nurse Shark Habitat

A gray nurse shark photographed at Fish Rock Cave.

A gray nurse shark photographed at Fish Rock Cave.

The New South Wales Department of Environment & Conservation (NSW DEC) has been using a 125 kHz GeoAcoustics GeoSwath Plus wide swath sonar system for habitat mapping in the state’s network of marine protected areas. The maps produced have proved invaluable in the planning process for two new parks announced last year which come into effect during the first half of 2007.

The swath sonar system has been used extensively at Broughton Island, Port Stephens-Great Lakes Marine Park, a site where the endangered gray nurse shark (Carcharias taurus) gathers. Prior to formation of the marine park, the species had been protected by a 500-meter fishing exclusion zone centered on an area of guttered, high-profile reef east of the island. The sonar data collected by the NSW DEC has contributed to the inclusion of many reefs south and east of the island within sanctuary and/or habitat protection zones for the new marine park.

Tim Ingleton, Environmental Scientist at DEC commented “We have found the GeoSwath Plus system to be a powerful tool for this mapping work. The software allows the production of high quality bathymetric grids very quickly. We have also been able to achieve excellent sidescan mosaics with the use of GeoAcoustics GeoTexture package.”

An additional aspect of this work is that DEC is using both the bathymetry and sidescan outputs with spatial data in GIS packages to help to classify habitat type.

Use of the swath sonar equipment continues with a new program due to begin in July 2007 and run for the next two years. This project involves habitat mapping for the state’s coastal Catchment Management Authorities, focusing on sections of the New South Wales coast to help in the understanding of the biodiversity associated with shallow (<80m) subtidal reefs in coastal waters.

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