The importance of habitat temperatures for growth in the tropical cichlid Tilapia rendalli Boulenger

Like many cichlids living in shallow tropical freshwater systems of Africa, Tilapia rendalli exhibit a marked daily movement into warm shallow water during the day and return to cooler, deeper water at night. Such movements have an important impact on the growth of juvenile fish. Growth is enhanced by this movement and is predicted to be optimal if the fish occupy water with a temperature of 30°C during the day but retire to nocturnal habitats with temperatures of 18°C. The reasons for this phenomenon are discussed using a bio‐energetic model incorporating measurements of feeding intensity, metabolic energy demands and assimilation efficiencies at temperatures ranging from 18°C—3°C and the ecological implications discussed using examples from natural systems.