Some Considerations of Population Dynamics and Economics in Relation to the Management of the Commercial Marine Fisheries

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Abstract
Mathematical models of sea fisheries are developed relating production to effort expended in catching the fish. It is shown that for a fishery where catch and population-increase are in equilibrium, the curve of production rises from zero with increasing effort to a maximum and then, as effort further increases, declines again to zero. The sustained yield, therefore, cannot be increased by indefinitely increasing effort. In some fisheries the effort is insufficient to produce this maximum; in others the effort is too great, and less than the maximum is harvested. Considering the value of the fish and the cost of the effort, it is shown mat for greatest economic yield the catch may often fall below the maximum sustained yield in pounds of fish. The question is raised as to whether sea fisheries should be managed on the basis of greatest yield of protein to a protein-hungry world, or on the basis of greatest economic and social benefit to the fishermen. It is concluded that the former basis is the more desirable, especially in sea fisheries exploited by several nations among which costs of effort and values of fish vary, thus making management on the latter basis virtually impossible.