Project overview: Habitat and population assessment of giant crabs (2003 - 2005)

This is the CSIRO portion of the collaborative Tasmanian Aquaculture and Fisheries Institute, University of Tasmania (TAFI)/CSIRO Marine Research Project titled 'Understanding Shelf-break Habitat for Sustainable Management of Fisheries with Spatial Overlap', which aimed to map and understand shelf-break seabed habitats (~150-350m depths) around Tasmania, Australia, which is an area of interaction between two fishery sectors, giant crab trappers and finfish trawlers. Both of these have been expanding over the past decade, with potential of impact to target species abundance, habitat structure, and ecosystem structure. This project aimed to research the habitat effects of these activities over the period 2003-2005 through sampling of fished and unfished areas using video transects, multi-beam acoustic swath mapping, and collection of physical samples using sediment grabs and benthic sleds, using chartered vessels and a voyage of the National Facility FRV Southern Surveyor in 2004. Specific objectives for the giant crab (Pseudocarcinas gigas) habitat survey are as follows: - define and map giant crab habitat on the shelf edge, at several key locations off the Tasmanian east and west coasts; - detail distribution of giant crabs in relation to habitat features; - evaluate ecosystem links between habitats; - evaluate the vulnerability of habitat to damage by fishing (trawls and pots); and - evaluate the ability to obtain fishery independent information by video on the abundance, sex ratio, condition and size of giant crabs. The CSIRO portion of the work comprised a series of four surveys to assess the seabed habitats of the giant crab at the edge of the continental shelf around Tasmania.
The image annotations collected for this project have been added to the Oracle data base BHIMAGE and the associated videos and still images have been archived as described in MarLIN record 14436 'Benthic Habitats Video Image Archive'.