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.

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Changes that occurred in sea surface and some deeper temperatures, surface winds, currents, plankton and some dominant crustacean (rock lobster Jasus lalandii), molluscan (squid Loligo vulgaris reynaudii and abalone Haliotis midae), fish (anchovy Engraulis capensis, pilchard Sardinops oce/latus, Cape hakes Merluccius spp., sole Austroglossus pectoralis, kingklip Genypterus capensis and various species of linefish) and seabird (Cape gannet Morus capensis) resources in the Benguela ecosystem in the 1980s are documented. Although fishing had a clear influence on changes in some of the resources, a wide spectrum of organisms, from plankton to top predators, were influenced directly or indirectly by the abiotic environment. Concurrent changes in many of the resources suggest that the same environmental change may impact on more than one. Simultaneous change throughout the Benguela system indicates that environmental forcing sometimes takes place over wide geographic areas. At the northern and southern extremities of the Benguela system, responses to environmental change may be different because processes through which the change is mediated are different.Verandering wat plaasgevind het in die see-oppervlak-en sommige dieper temperature, oppervlakwinde, strome, plankton en sommige hulpbronne soos skaaldiere (kreef Jasus lalandii), weekdiere (tjokka Loligo vulgaris reynaudii en perlemoen Ha/iotis midae), vis (ansjovis Engraulis capensis, sardyn Sardinops oce/latus, Kaapse stokvis Merluccius spp., tongvis Austroglossus pectoralis, koningklip Genypterus capensis en verskeie lynvisspesies) en seevoels (witmalgas Morus capensis) in die Benguela-ekostelsel in die 1980s word gedokumenteer. Ofskoon die vissery 'n duidelike invloed op veranderinge in somrnige van die hulpbronne gehad het, is 'n wye spektrum organismes, van plankton tot spitsroofdiere, regstreeks of onregstreeks be"invloed deur die nie-Iewende omgewing. Gelyktydige veranderinge in baie van die hulpbronne dui daarop dat dieselfde omgewingsverandering op meer as een van hlllle 'n uitwerking mag he. Gelyktydige verandering dwarsdeur die Benguelastelsel laat dink dat omgewingsforsering soms oor wye geografiese gebiede plaasvind. By die noorder-en suider-uiteindes van die Bengllelastelsel kan die reaksies op omgewingsverandering verskil omdat die prosesse waardeur die verandering teweeggebring word, verskil. 1992 4 J 2 J

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