The biology of Carangidae (Teleostei) in Natal estuaries
The occurrence and abundance of 17 species of Carangidae in Natal estuaries are described. The following six species are of significance in the estuarine community: Caranx ignobilis, C. melampygus, C. papuensis, C. sexfasciatus, Lichia amia and Scomberoides lysan . Only juveniles and subadults utilize estuaries. The time of recruitment, growth rates and feeding biology of the six species were investigated. Among the juveniles, C. ignobilis and C. sexfasciatus are mainly piscivorous on a variety of small estuarine fishes and estuarine dependent juveniles of marine species, while C. melampygus, C. papuensis and S. lysan filter feed on mysids and juvenile penaeids. Subadults of all species are piscivorous, although C. papuensis and S. lysan retain a suitable gill raker structure for filter feeding and a proportion of their diet consists of mysids and penaeids. The salinity and turbidity preferences of each species were investigated. All are euryhaline but C. melampygus, C. papuensis and 5. lysan are only found in clear water. It is suggested that the more widespread estuarine distribution of juvenile C. sexfasciatus and C. ignobilis may be related to their turbidity tolerances. The role of carangids in Natal estuaries is discussed in relation to their ecological significance in estuaries as predators and their degree of estuarine dependence.