Blue swimmer crab (BSC) post-harvest flesh quality in Shark Bay WA is a concern to Abacus Fisheries. 10-20% of crab flesh is unsaleable (i.e. mushy) after cooking, equating to losses of between $250,000 and $500,000/year (Fishery value:$1.8-2.5M/yr).

Mushiness in BSC may be caused by proteolytic enzymes escaping from the hepatopancreas post-mortem and breaking down adjacent muscle tissue (Slattery et al 1989). This can occur if crabs die before cooking (Stevens, 1995) or cooking times are too short or temperatures too low. Slattery et al found that cooking temperatures of greater than 70oC for 10 minutes reduced the problem.

Notwithstanding the above, the problem persists in Shark Bay despite cooking torpid live crabs for 13 minutes at 95-97oC. This suggests further information is needed to resolve the issue. For example, muscle water content is highest in postmoult/early intermoult crustaceans (Musgrove, 2001), possibly contributing to mushiness on processing. Shark Bay crabs moult throughout the year although peaks appear around January/February, May/June and July/August (P. Jecks. pers. obs.).

Parasite infestation (i.e. microsporidians especially Ameson sp.) in harvested crabs may also result in mushy flesh after cooking (Shields and Overstreet, 2007). Stress may also affect tissue quality, influenced by predators (eg. octopus), harvest process, boat well overcrowding or sub-optimum post-harvest chilling. The effect of gut-fullness is also unknown; fuller guts may generate greater protease activity, leading to more postmortem tissue breakdown.

Abacus Fisheries has developed new markets and products, yielding significant premiums and substantial increases in BSC beach price. However, the occurrence of mushy flesh can slow production through excessive time spent checking for flesh quality. This impacts profitability and can threaten the super-premium fine dining market position enjoyed by Abacus Fisheries products. There is a need to clarify the causes of flesh deterioration so alternate harvesting or processing strategies can be implemented.