Measuring condition of lobsters (Jasus edwardsii) to improve management of harvesting around periods of high transport mortality

Losses of up to 10% of lobsters during live transport have been observed in Tasmania around the time of season openings in mid-November. The fishing industry, including processors and operators are seeking ways to avoid this mortality. There is a general industry perception that brindle lobsters are associated with greater mortality rates. The main objective of this study was to quantify differences in condition of pale and red male lobster stocks in four different fishing areas of Tasmania that could be associated with different levels of mortality. Condition can be divided into several categories including nutritional condition, physiological condition, and health. All three categories can contribute to differences in vulnerability to transport stress therefore a holistic approach incorporating assessment of tissue composition, organic and inorganic constituents in the haemolymph and total haemocyte count was used. Nutritional condition (Brix index, hepatopancreas lipid content, abdominal muscle C:N ratio and dry matter content) and physiological condition (haemolymph urea, magnesium, potassium and bicarbonate content) were not affected by lobster colour but significantly differed among sites inside study areas. Indicators of health showed no significant differences between lobster colours or among sites. These results indicated that the overall condition of lobsters was not significantly different between red and pale lobsters. Variation in condition is greatest at a site level (fishing shot) strongly suggesting that specific biotic and abiotic conditions (i.e. depth, density of conspecifics, predator risk, competition) rather than broad scale latitudinal or regional patterns are driving condition of lobsters.