Stress indicators in marine decapod crustaceans, with particular reference to the grading of western rock lobsters (Panulirus cygnus) during commercial handling

Good transport survival of western rock lobsters (Panulirus cygnus) is ensured by rigorous selection of healthy lobsters prior to packaging for transport. The rejects are attributed to stress during harvesting and handling. A major stresser, of variable severity throughout the fishery, is the storage and transport of the lobsters out of water with accompanying effects of temperature, disturbance and tail-flipping exercise on metabolic rate. Pointers to apparent fatigue or injury in weak lobsters may be found in lobster haemolymph. Published literature suggests a number of parameters that might prove to be predictors of mortality in P. cygnus, but these will have to be examined in detailed physiological studies. Information is also required from tissue metabolism and pathology to complete the picture. If the symptoms are the result of previous stress, then one obvious approach is to sample rock lobsters at key points along the harvesting and handling process, in conjunction with sampling of normal or 'baseline' lobsters and laboratory stress trials. Practical stress indicators, once identified, can be used both to test existing screening methods and in studies aimed at changing handling practices to reduce stress.