The Biology and Culture of Tilapias

Feeding, Metabolism and Growth of Tilapias:

Some Quantitative Considerations

M. S. CAULTON

King Prawns (Put.) Ltd.

P. 0. Box 135

Kan'ba

Republic of Zimbabwe

CAULTON, M.S. 1982. Feeding, metabolism and growth of tilapias: some

quantitative considerations, p. 157-180. In R.S.V. Pullin and R.H. Lowe-

McConnell (eds.) The biology and culture of tilapias. ICLARM Conference

Proceedings 7, 432 p. International Center for Living Aquatic Resources

Management, Manila, Philippines.

Tilapias are strongly thermophilic with an eccritic thermal range varying

from 30°C to 36OC depending on species. Natural populations of tilapias

often show a diel movement which mirrors the diel thermal fluctuation of

shallow inshore waters of lakes, pans or inundated river flood plains. The

movement of young tilapias is shoreward, toward warm water, during the day

and away from the shore during the night as the shallows cool rapidly.

Metabolic energy demand, being a function of both temperature and mass, is

strongly influenced by the thermophilic behavior of tilapias living in natural

waters. Tilapias that feed on aquatic macmphytes demonstrate that food

intake is related to both body mass and environmental temperature. Assimila-

tion efficiency increases with increasing temperature. The cost of food

processing is a function of both food quality and quantity but is also in-

fluenced by environmental temperature. The increased net gain in assimilated

energy at high temperatures may be almost offset by the increased cost of

food processing at comparable temperatures.

When considering these factors and formulating a simple energy budget it

Jis clear that high daytime temperatures coupled with lower nighttime temper-

atures lead to an optimal use of energy resources and results in increased

growth potential. Aquaculturists should take note of such physiological

optima and with careful design of ponds and water management could create

a diel temperature variation resulting in enhanced growth potential and

decreased food conversion ratios.

Introduction

Rapid growth rates, good productivity per unit volume of water and
economic, efficient food conversion make the tilapias a suitable fish for the
needs of the modem aquaculturist. This group of fish made an early appear-
ance in the field of aquaculture, but the rather premature enthusiasm waned
somewhat when many of the earlier ttials failed to come up to expectations.
Today, however, significant advances have been made in the basic under-
standing of the biology of these fish, and controlled production is becoming
increasingly successful. Notwithstanding this recent upsurge in the importance
of these fish to aquaculture, there still remains a paucity of information
which would contribute to our understanding of their physiological and