Methods for monitoring abundance and habitat for northern Australian mud crab

Project leader Tracy Hay; principal investigator Dr Neil Gribble; co-investigator Stephen Bailey
Research centre:
Northern Fisheries Centre, Cairns

Report summary

A significant achievement of this project has been the completion of mapping of coastal wetland habitats using remote sensing techniques, which provided complete broad-scale coverage of mud crab habitats in the Northern Territory and Queensland. A major outcome of this work has been the incorporation of the mapping into a geographical information system (GIS) permitting a much wider application across a variety of natural resource management agencies and issues. The updated Queensland maps are now available electronically to the public via the Department's website CHRIS.

The identification and quantification of northern Australian coastal wetland habitats will benefit a broad range of northern Australian inshore fisheries. Survey and analysis methodologies, based on mark-recapture techniques, have been developed to estimate mud crab density for two key habitat types in northern Australia. Density estimates for
each habitat type were extrapolated across adjacent regions in each state providing the first broad scale estimates of mud crab stock size.

A direct and recent output from this work has been the use of preliminary biological and fishery data, to compare trends between years for Queensland and Northern Territory mud crab fisheries, during a recent fishery assessment. This fishery assessment was convened in July 2004, to investigate the reduction in commercial mud crab catch in the Northern Territory. Negotiations on adjustment to the Northern Territory management arrangements are in progress.

Declines in catch and catch rate were observed in both the Northern Territory and Queensland Gulf of Carpentaria (GOC) surveys over the two years of this study. This suggests large-scale environmental drivers influence mud crab recruitment success, at least for the Gulf region. Estimated abundance for this region in the NT indicates a very high proportion of the legal-sized mud crab stock was removed in 2003.

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The final report can be obtained from the Fisheries Research Development Corporation (FRDC). The report number is 2000/142

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Last updated 13 November 2012