Title: CHEMICAL ATTRACTION CAUSING AGGREGATION IN THE SPINY LOBSTER,<i>PANULIRUS INTERRUPTUS</i>(RANDALL), AND ITS PROBABLE ECOLOGICAL SIGNIFICANCE
Abstract: Field and laboratory experiments were performed to determine the mechanisms of aggregation by the lobster, Panulirus interruptus. Capture-frequencies by unbaited traps, modified to simulate refuges by allowing lobsters to both enter and exit, were found to fit a negative binomial (κ < 0.5) rather than a Poisson distribution. Such over-dispersion in the capture of lobsters was not fully attributable to environmental factors, suggesting that conspecific attraction may have been occurring. Laboratory trials conducted in a large rectangular tank (9.0 m x 2.4 m x 1.0 m) demonstrated that substances released by both sexes are highly attractive to conspecific males and females alike, resulting in aggregation. Abalone muscle, a potent feeding attractant to P. interruptus, was ineffective in initiating aggregation while dead lobsters, excised lobster thorax and abdominal muscle were all avoided. The tendency to aggregate changes during the course of a night, and aggregations are probably formed just before dawn and maintained until dusk. Results are consistent with a hypothesis that conspecific interactions facilitate anti-predatory defense and avoidance in Panulirus.