Moulting behaviour of the tiger prawns Penaeus esculentus (Haswell)

Abstract

The moulting behaviour of P. esculentus was investigated using time-lapse video equipment for several days either side of ecdysis. An ethogram was compiled using data from 1 h before to 6 h after ecdysis and the behaviour was divided into five discrete and nine continuous acts. Discrete acts occurred mainly during pre-ecdysis. Ecdysis in the laboratory and in the field was nocturnal (pooled mean time of ecdysis 2230 h) and rapid, occupying a mean time of 18.1 s. Comparison of moulting behaviour in an aquarium and in a pool of diameter 6 m indicated that confinement in a small space may produce behavioural artefacts including swimming before ecdysis and lying on the side on the bottom following ecdysis. Immediately after ecdysis the prawns flicked, swam, then walked for several metres after which they remained stationary on the surface of the substrate for a mean of 6 h before burying. In all, 70% of prawns did not feed on the night of ecdysis. P. esculentus exhibited a reduced emergence time compared with intermoult prawns on the night of the moult and on nights preceding and following ecdysis. These findings suggest that P. esculentus may have a reduced catchability in trawls on these nights.