The effect of conspecific interaction on survival, growth and feeding behaviour of early juvenile tropical spiny lobster Panulirus ornatus

Abstract

Behaviour underpins many facets of the performance of animals in aquaculture. By manipulating culture systems to segregate or allow particular aspects of conspecific interaction, we found physical interactions between P. ornatus individuals to be essential for better culture performance. Three culture types were used to control conspecific interactions: isolated culture (individual vessels) excluded all conspecific interactions, separated culture (lobsters cultured in adjacent cages) excluded physical interactions, and communal culture allowed for all interactions. Two water exchange rates were introduced to investigate the influence of chemical cue intensity on growth and survival. Time-series photography was used to determine the feeding behaviour and preference for different feeds including mussel gonad, commercial prawn feed and moist feed. The experiment showed improved growth and moulting frequency in communally cultured lobsters. These results suggest that direct physical contact between conspecifics is required to optimise growth of lobsters, which may be related to the complex social structures of this gregarious species. Behavioural observations of two juvenile instars (2 and 4), revealed circadian rhythm of interactions with feeds, feed preferences and intake. Observations revealed differing behaviours between the different culture types, where lobsters reared in separation displayed higher level of interactions with feeds; however this was not associated with higher feed intake. Observations of two juvenile instars (2 and 4) exhibited increase of daylight activity (interactions with feeds and feed intake) in older lobsters (instar 4).