Haemolymph chemistry of tropical rock lobsters (Panulirus ornatus) brought onto a mother ship from a catching dinghy in Torres Strait

Abstract

For export of live Panulirus ornatus from northern Queensland, divers catch the lobsters by hand and keep them in small tanks on dinghies before draining the tanks and returning at speed to a mother ship that has a larger storage tank. The lobsters are sometimes too weak for export. The physiological state of lobsters stored in a tank on the mother ship was studied by measuring the concentrations of L-lactate, D-glucose and ammonia in the haemolymph. Oxygen levels in the dinghy tanks were normally acceptable but fell rapidly below 50% saturation when flow was stopped and the tank was draining. The concentration of lactate in the haemolymph of lobsters arriving from the dinghy was 16.4 ± 5.7 mmol L^-1 (mean ± s.d.,n = 9); this fell during storage on the mother ship. On the mother ship, serum concentrations of calcium, potassium and magnesium ions all increased, haemolymph glucose concentration increased slightly and then decreased, and ammonia concentration did not change. Future work may identify which aspects of prior handling are responsible for the elevated lactate concentrations in captive lobsters, but improvements could be made meanwhile to water flow through the dinghy tanks.