Food and Growth of Fishes.: III. Relations Among Food, Body Size, and Growth Efficiency

Reexamination of published data on growth and feeding of fishes shows that when fish are fed on one type of food, the logarithm of the gross growth efficiency (log K) decreases with increase in rations. For a number of species and experimental situations this relation is adequately described by the linear equation[Formula: see text]whence[Formula: see text]where ΔW is the growth, R the rations intake during the period of time Δt, and a and b are the parameters fitted to the linear form of the equation. With a single food-supply level, rations are highly correlated with body weight so that either one may be used to predict the growth efficiency. However, comparison with experimental situations which induce changes in rations intake at given body size, suggests that body size is not the determining factor as long as environmental conditions are within the normal biokinetic range. That is, the basic pattern of distribution within the animals of the energy intake is described by a knowledge of the rate of intake and two parameters.The action of various environmental factors appears to be reflected in this equation in different ways. In the experiments examined changes in temperature, which are known to affect the level of total metabolism, affected the value of R but the parameters a and b remained unchanged. That is, temperature changes appeared to affect only the energy turnover rate, not the distribution of energy in the fish. By contrast, changes in factors such as salinity and metabolic wastes, which are known to affect th...