The Culture of Tilapia Nigra (Cunther) in Ponds IV-The Seasonal Growth of Male T. Nigra

Abstract

The growth rate of male Tilapia nigra is neither constant throughout life, nor from month to month. It decreases asymptotically in length as the fish grows older, and varies from month to month according to fluctuations in external environmental conditions, weight being more affected than length in the latter instance. The most important external factor is undoubtedly the water temperature at which the fish live; rises and falls in mean temperatures of only a few degrees causing marked increases or decreases in weight achieved, respectively. Water temperature is in itself much affected by other weather conditions, and is not necessarily maximal in months of maximum sunshine owing to increased wind speeds and evaporation rate in such months. Rainfall may in itself also affect fish growth directly, though this is not fully established yet. In the environmental conditions present at Sagana, male T. nigra show two good growing periods and two poor growth periods every year.