Review of relationships between life history stages of the western rock lobster, Panulirus cygnus, in Western Australia

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The western rock lobster, Panulirus cygnus, fishery in Western Australia has over 30 years of time series data on spawning stock estimates, abundance of puerulus settlement and juvenile abundance, catch and fishing effort, and environmental factors affecting recruitment. This review updates the relationships between different life history stages that have provided some important insights for the stock assessment and management of this fishery. The study highlights the management uses of the catch prediction relationship, up to 4 years ahead, of the commercial rock lobster fishery as well as that of the licensed recreational fishery based on the level of puerulus settlement. The relationships between catch and puerulus settlement indicate that the density-dependent relative survival at different levels of puerulus settlement can vary by a factor of 5. Oceanographic modelling of the 9–11-month larval phase of the lobster suggests that ocean currents completely mix the larvae from all spawning regions, while tagging of juveniles and adults confirms that the stock forms a metapopulation consisting of subpopulations of juveniles and adults that generally undergo migrations of less than 50 km. This emphasises the importance of examining the spawning stock over the whole fishery when assessing the stock–recruitment relationship. The south-flowing Leeuwin Current significantly influences the level and spatial distribution of the puerulus settlement along the coast.