The behavioural interactions of carangids with their prey have been examined on the forereef slope of Aldabra Atoll, Indian Ocean. From underwater observations and from fishing data, Caranx melampygus and C. ignobilis are shown to be predominately piscivores. Slight differences in the sex ratios occurred when compared with earlier work, although length distribution of trolled specimens match very closely. By contrast underwater observations indicate that many more small C. melampygus occur on the reef slope than are caught by trolling and suggest this method of capture is highly selective. The literature ascribes the association of small predatory fish to larger ones with a scavenging role, but present observations suggest that it provides a mechanism whereby small fish can approach and exploit the disorientation of prey during hunting episodes. Other types of predator association are discussed.