ASPECTS OF THE BIOLOGY AND LIFE-HISTORY OF WHITE STEENBRAS LITHOGNATHUS-LITHOGNATHUS IN SOUTHERN AFRICA

Data on the seasonal abundance, size composition, reproduction, growth and diet of Lithognathus lithognathus are presented to outline the life history of the species. Spawning appears to be localized on the Transkei and Eastern Cape coasts during a short period in late winter. Small juveniles (< 50 mm) enter estuarine nursery grounds along the Cape coast between September and November, remaining there for at least their first year of life before re-entering the marine environment. The post-estuarine juveniles (> 150 mm) are semi-resident in the surf zone of sandy and mixed shores for about five years until maturing at a length of 650 mm, when they commence annual migrations. During autumn and early winter these mature fish migrate eastwards to near the north-eastern limit of their distributional range, to spawn during late winter. The return migration takes place during spring and large numbers of mature fish arrive in the South-Western Cape during summer. The high degree of estuarine dependence, the confinement of juveniles and subadults to the surf-zone, the large size at maturation and the predictable aggregations of mature individuals in particular areas are considered to render L. lithognathus particularly vulnerable to estuarine degradation and exploitation by fishermen.