Queensland's fishery for blue swimmer crabs is managed conservatively. Fishers are allowed to take only males, and the size limit (15 cm carapace width) is set at above 85% of L infinity. South Australia, Western Australia and New South Wales currently market female crabs. There is considerable contrast available between management regimes and therefore scope to consider the possible economic gains and biological risks associated with these alternative strategies.
Stock assessment leading to the development of optimal management strategies was one of the key objectives of the National Blue Swimmer Crab Research Strategy. Therefore, current information on growth, mortality, movement and size structure of the catch in Queensland (both commercial trap and trawl sectors, and the recreational sector) needs to be collected and incorporated into yield models and more comprehensive population models which allow the risks and gains of alternative management strategies to be evaluated.
The only significant research into Queensland blue swimmer crab stocks that has been conducted since 1987 (See Reference List in Background) has been the analysis of daily commercial catch and effort from logbook records (CFISH). However, there has been concerns about the accuracy of the CFISH crab data. There have also been major changes in the fishery, including reported increases in trawl catches and a decline in both catch and CPUE in the trap fishery. The fishery has also expanded into new areas which were not covered in previous research and is in fact still expanding.
Megalopa collectors have proved successful for collecting portunid megalopa in North America (Lipcius et al, 1990; Olmi, 1990; Olmi et al 1995) and are a routinely used method of fishery indepenndent survey in the US blue crab (Callinectes sapidus) and other crab fisheries which have similar life histories to our blue swimmer crab. Similar methods are used in predicting year class strength of the Western rock lobster and other fisheries in Australia. There is a need to undertake pilot work to develop and trial collectors for quantitatively collecting blue swimmer crab megalopae. If blue swimmer crab megalopae can be collected on artificial collectors then these techniques may have application in a fisheries context, as they are in other crab fisheries around the world.
