ABSTRACT
The growth rate and fatness of fish depend upon the amount of food available and its nutritive value. In fish culture, food is provided either by direct feeding or by enriching the water so as to promote planktonic growth. Fish food is much richer in the lakes than in rivers. Species composition of fish food in reservoirs is intermediate between that in rivers and that in lakes. The number and quantity of natural food species fluctuate seasonally and vary according to the type of water body. In rivers which freeze in winter, seasonal changes of water conditions are very distinct. The growth and development of organisms in a lake may be affected by physical, chemical, and biological factors. Physical factors vary seasonally and according to geographical areas. Chemical and biological factors are affected by physical factors. Major physical factors are temperature, light, and current velocity.
