Distribution of newly settled western rock lobsters Panulirus Cygnus

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Abstract
Little is known about the biology of the post-puerulus stage (i.e. individuals < 25 mm carapace length) of the commercially valuable western rock (spiny) lobster Panulirus cygnus, and few have been found in the field. In the present study, the natural habitat of post-pueruli was discovered through intensive diving surveys. Additional studies of habitat preference were carried out using a variety of designs of artificial habitats and the response of the post-pueruli to transferral between shelters was evaluated. Post-puerulus P. cygnus were found to shelter in small holes on the face, in ledges and in caves on coastal limestone reefs. They apparently preferred shelters with additional cover, typically seagrass and/or algae. Movement between shelters appeared common because 50% of monitored shelters were occupied for only a single day. Post-pueruli occurred in groups of up to 100 individuals, although 75% were solitary. There was a trend for larger post-pueruli to be gregarious. Two designs of artificial shelter were successfully utilised by post-pueruli: those made of ''Tanikalon'' which resembled algae or seagrass, and those that consisted of holes in limestone blocks covered by seagrass. In transferral experiments, at least 50% of post-pueruli refused to enter or remain in new shelters after transfer from their previous shelters. This may be influenced by the method of release. Discovery of the natural habitat of post-puerulus P. cygnus means that it is now possible to study other aspects of their biology and population dynamics. Results of the transfer experiments indicate that future research is needed to determine the best release method to minimise rejection of new shelters. The successful utilisation of artificial habitats suggests that these habitats may have potential to enhance the survival of post-pueruli in areas where shelter is limited.