BEHAVIOR AND GROWTH OF CAPTIVE SPINY LOBSTERS (PANULIRUS-ARGUS) UNDERTHE RISK OF PREDATION

The behaviour and growth of captive spiny lobsters (Panulirus argus) u nder and not under the risk of predation was investigated in four 9-m( 2) sea enclosures: two 'predator enclosures' (P1 and P2) into which on e predator, the triggerfish Balistes vetula, was introduced; and two ' non-predator enclosures' (NP1 and NP2). Each enclosure contained a 1-m (2) artificial shelter, and lobsters were provided with food ad libitu m for 45 days, measured then left for a further 30 days with a reduced food supply. Inter-and intraspecific interactions and shelter use wer e recorded by means of underwater observations during day and night. D aytime shelter use by lobsters and fish was highest at noon and in the early morning. Activity of lobsters outside the shelters peaked aroun d midnight in all four enclosures. Lobsters in P2 showed more activity and less shelter use than did those in all other enclosures, More pre dator-prey interactions were recorded in P1 than in P2, whereas intras pecific interactions were more prevalent in P2 than in the other three enclosures combined. Growth of lobsters was significantly higher only in NP1. The difference in lobster behaviour and survival between the two predator enclosures may be associated with the initial timing of s helter occupancy by the predators.