The Relationship between Catch Rates and Abundance in Fisheries

Abstract

Distributions of catches for given effort in fisheries typically show much greater variability than would be expected on the basis of constant catchability models. Incorporation of this extra variability into simple models for fisheries leads to the prediction of a nonlinear relationship between catch rates per unit fishing effort and the abundance of fish. Given fractional changes in abundance are predicted to yield lesser fractional changes in catch rates. The extent of this nonlinearity can only partially be inferred from the distribution of the catches.