Larval ecology of the Western Australian marine crayfish, with notes upon other panulirid larvae from the eastern Indian Ocean

Abstract

The Western Australian marine crayfish is now regarded as Panulirus longipes cygnus (George). Larvae could not be distinguished morphologically from those of tropical subspecies. The identity of the various stages of phyllosoma and puerulus larvae of the species has been established, and an outline is given of the seasonal occurrence and growth of larvae. The eggs of P. longipes cygnus hatch during summer, larvae being released along the coast into water of relatively high salinity (generally exceeding 35.4‰). Offshore surface wind drift during summer is proposed as the means by which the newly hatched phyllosoma larvae are transported away from the coast. It is not clear how late-stage larvae return to the coast; there is some evidence that their behaviour might change with regard to depth of occurrence and also diurnal vertical movements. The timing of the larval cycle varies from year to year; final-stage larvae probably cannot return to settle on the coast until the disappearance of the low salinity tropical water which extends down the west coast of Australia each winter. The importance of larval surveys as a means of estimating the size of the brood stock and to forecast the strength of a year class is discussed. Other species represented in the plankton of this area as phyllosoma larvae are listed, and some information given on the morphology, distribution, and dispersal of phyllosoma larvae tentatively identified as P. penicillatus.