Review of the Fishery for and Biology of the Cape Rock Lobster Jasus lalandii with Notes on Larval Recruitment

Abstract

The South African fishery for the rock lobster Jasus lalandii currently yields about 3800 metric tons (8.4 million animals) of which more than 90% are males. Males grow much faster than females, and a size limit which is fairly large in relation to the size and age at maturity protects females from exploitation for most of their lifespans, thereby ensuring a high level of larval production from the population. Exploitation rates in the fishery are controlled by means of quotas on fishing companies, as well as catch limits on individual fishing grounds. Quotas are reassessed annually to maintain instantaneous fishing mortality rates of approximately 0.3 on all grounds. Catch rates on most grounds have been increasing since area catch limits were introduced in 1980, and seasonal averages now vary between 4 and 12 kg∙trap-day−1. Although annual indices of puerulus larval recruitment are not available, and the stock–recruitment relationship is unknown, it appears that relatively stable yields can be maintained despite fluctuations in puerulus recruitment. Density-dependent regulatory mechanisms operative in juvenile and young adult stages tend to dampen large variations in the numbers of adults entering the fishable size range each year. Variations in puerulus recruitment are likely to result from changes in the paths and velocities of extensive offshore currents which eventually return larvae toward the coast of South Africa after many months of pelagic existence.