Fluctuations of year-class strength and recruitment in the western rock lobster Panulirus longipes (Milne-Edwards).

Abstract

Settlement of puerulus larvae on collectors composed of artificial seaweed and measurements of density of young juveniles on 'nursery' reefs show wide fluctuations in year-class strength, recent settlement from the spawning crop of 1973-74 being particularly high.

Owing to restricted holding capacity of the shallow 'nursery' reefs (mainly due to limited food supply), density-dependent mortality reduces most year-class strengths to similar levels by the time juveniles reach 5 years of age. Particularly weak year-classes have been shown to be associated with poor catches from the coastal 'white' fishery at the opening of a fishing season. The applications of these findings to the management of the fishery are discussed.

In theory, part of the wastage resulting from excess settlement of larvae in certain areas might be saved by transplanting to less crowded reefs or by mass-rearing in ponds, without diminishing recruitment from those left on the now overstocked reefs.