Field observations on a school of Lutianus monostigma have been made off Aldabra in the shallow reef environment. The school does not exhibit any obvious response to temperature. The response to current is the main factor that determines school orientation and position in the channel. Longshore movements are performed but their function is not known. The morning and evening dispersal may be associated with changes in light intensity and/or the crepuscular feeding habits. The response to predators depends upon the behaviour of the predator, its species and size. Other factors affecting the school in their natural environment are described.