Improved Estimates from the Schaefer Production Model: Theoretical Considerations

Abstract

The Schaefer production model is converted to a form directly applicable to a data stream of annual fishing efforts and catches. The new version is also stochastic; that is, it allows for unpredictable influences on the fishery. A new method for estimating optimum effort and catch results from this analysis, as well as a way of measuring uncertainty in these estimates. Equations are given for predicting the next annual catch and assigning confidence limits to this prediction. Linear and nonlinear regressions are proposed for this analysis, and the relationship between them is rigorously demonstrated. The linear method leads to estimation formulas simple enough to be applied on a programmable pocket calculator. Key words: Schaefer model, production model, stochastic model, management, fishing effort, catch per unit effort, maximum sustainable yield