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 stressor, 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.

Instances of morbidity amongst rock lobsters (Panulirus cygnus) arriving at factories in Western Australia (WA) have been attributed to stress during post-harvest handling. This study used discriminant analysis to determine whether physiological correlates of stress following a period of simulated post-harvest handling had any validity as predictors of future rejection or morbidity of western rock lobsters. Groups of 230 western rock lobsters were stored for 6 h in five environments (submerged/flowing sea water, submerged/ recirculating sea water, humid air, flowing seawater spray, and recirculated seawater spray). The experiment was conducted in late spring (ambient sea water 22°C), and repeated again in early autumn (ambient sea water 26°C). After 6 h treatment, each lobster was graded for acceptability for live export, numbered, and its haemolymph was sampled. The samples were analysed for a number of physiological and health status parameters. The lobsters were then stored for a week in tanks in the live lobster factory to record mortality. The mortality of lobsters in the factory was associated with earlier deviations in haemolymph parameters as they emerged from the storage treatments. Discriminant analysis (DA) of the haemolymph assays enabled the fate of 80-90% of the lobsters to be correctly categorised within each experiment. However, functions derived from one experiment were less accurate at predicting mortality when applied to the other experiments. One of the reasons for this was the higher mortality and the more severe patho-physiological changes observed in lobsters stored in humid air or sprays at the higher temperature. The analysis identified lactate accumulation during emersion and associated physiological and haemocyte-related effects as a major correlate of mortality. Reducing these deviations, for example by submerged transport, is expected to ensure high levels of survival. None of the indicators tested predicted mortality with total accuracy. The simplest and most accurate means of comparing emersed treatments was to count the mortality afterwards.

In this study, conducted in collaboration with the Western Australian rock lobster industry during the 1992–93 fishing season, daily records were made on morbidity and mortality of western rock lobsters, Panulirus cygnus, held in commercial shipping (export) cartons. The aims were to measure the rates of morbidity + mortality and to identify patterns of correlation of morbidity + mortality rates for a range of environmental variables recorded by the processors. In three processing units, the rate of morbidity + mortality in simulated live shipments averaged 5á2% (±0·6), with a highly significant difference (P<0·001) between processing units. Three factors, holding time in export cartons, ambient temperature within the export cartons and chilling period before packing lobsters, had the greatest influence on the rate of morbidity + mortality. Morbidity + mortality rate of animals held for 30–36 h (10·4 ± 2·3%) was twice that of animals held for 20–24 h (5·2 ± 0·6%). A positive significant correlation (r = 0·25, P = 0·001) was identified between morbidity + mortality rate and the internal carton temperature. Aprolongation of the chilling period was reflected by improved survival, possibly resulting from an anaesthesic effect of the chilling treatment.