Fishes exhibit a 'determinate' type of growth in short-lived species of warmer regions and an 'indeterminate' type in long-lived species of colder regions. Growth is measured in units of length and weight and is best represented as the specific growth rate. The relationship between weight and length provides an index of the state of well-being of a fish (condition factor 'K'). Growth could also be measured by using certain other criteria such as glycine uptake by scales, hepatosomatic index, RNA:DNA ratio and protein retention in the tissues. Nutrition, including the quality and quantity of food, plays a significant role in growth regulation. A number of environmental factors, such as temperature, oxygen concentration, salinity and photoperiod, influence the rate of growth. Recent data suggest that genotypes, hormones and physiological conditions of the individual are also equally important endogenous regulators of growth.