The trawl grounds for these fisheries probably coincide closely with very fine sand or mud (mean grain diameter <0.1 mm) sediment types, as described earlier for the east coast of South Africa, mud being the preferred habitat for these prawns (de Freitas 2004). Members of the family Sciaenidae (croakers; Fennessy and others, 2004) are prominent among the fishes in these mud-dominated shelf habitats, and can be considered indicators of the presence of prawns (Pauly and Neal 1985). Thus, in inner shelf waters associated with river mouths, members of the Sciaenidae and Cynoglossidae would predominate owing to their preference for turbid or muddy habitats, while Sparidae, Triglidae, Sauridae and Haemuli-dae are probably more predominant over inner shelf substrata with less mud.