Fundamental Relations among the Selections of Life History in the Marine Teleosts

Abstract

The modes of fluctuation in numbers of the marine teleosts have evolved in three directions. The first extreme is Subtype IA which makes short-period and irregular variation and the second one is Subtype IB which exhibits a large-scale and periodic change. The last one is Type II showing a small and steady variation. The species situated close to the extremes are sauries and sandeels, sardines and herrings, and tunas and flatfishes in the above order. Each type has selected the particular life history, corresponding to the environment inhabited. The selection of life history is the selection between two directions, i.e., one is to put the resources into the preservation of brood and the other is to pour them into that of nidividual. The inter-relations among the three types are shown as a three-type triangle and a given marine teleost occupies a position somewhere inside this triangle.