Recruitment and origin of penaeid prawn postlarvae in two South-east African estuaries

Input of postlarval stages into the penaeid prawn stocks of Natal, South Africa, was investigated by monitoring immigration into the St Lucia and Kosi estuaries. Five species, Penaeus japonicus Bate, P. indicus Milne Edwards, P. semisulcatus de Haan, P. monodon Fabricius and Metapenaeus monoceros (Fabricius) were recorded. Recruitment into the more northerly Kosi estuary, where offshore conditions are influenced by the south-flowing Agulhas Current, was totally dominated by P. japonicus. At St Lucia, at the northern end of the Tugela Bank, similar numbers of P. japonicus and P. indicus were recorded as well as smaller numbers of the other three species. The differences imply that the Tugela Bank provides the major postlarval input of commercially important species to St Lucia and suggests a greater degree of isolation of the Natal penaeid prawn populations than previously thought.