An Allocation Model of Growth and Reproduction in Fish

Abstract

A simple model is proposed to describe the pattern of allocation of resources into growth and reproduction. This model assumes that there is a fixed amount of surplus energy which may be channeled into either somatic or gonadal tissue. The change in weight or length of a fish can be predicted from this model from the surplus energy and the gonadosomatic index. Evidence is presented that in many species the gonadosomatic index can be assumed to be a constant. Surplus energy can also be estimated by inverting the growth equations. With this information it is possible to examine the consequences on Darwinian fitness of changes in the age at maturity or the allocation to reproduction as measured by changes in the gonadosomatic index. The allocation model is validated using data on the growth of American plaice, Hippoglossoides platessoides. It is shown that the reproductive strategy of American plaice cannot be accounted for on the basis of the trade-off between growth and reproduction.