A Concept of Growth in Fishes

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Abstract
The use of size as a basic determinant of growth rate is discussed and compared to analogous situations described in literature on other physiological rates. Ecological opportunity and physiological opportunity are visualized as the 2 interacting components that determine growth, both of which are entered at "threshold" sizes. The parabolic function, [image] is developed into a growth equation for linear dimensions and its application explored and discussed using steelhead trout and chinook salmon as an example. Significant differences in growth rate are found between life history types and sexes. The Chinook data are then treated on a lt+1, lt plot and it is shown how an apparent fit of the von Bertalanffy type growth equation can result from selectivity of fishing for the larger fish of any brood year. Two lines of research are indicated. (1) The independent measurement of the exponent x through study of size-specific metabolic rates, and (2) the relationship between total mortality rate and growth rate. Without this knowledge a satisfactory synthesis of growth rate into a yield equation cannot be achieved.

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