Is MSY an Adequate Foundation for Optimum Yield?

Abstract

Abstract Traditionally, maximum sustained yield (MSY) has been estimated from surplus production models. A second approach has been to calculate MSY as the product of average recruitment and maximum yield per recruit. These approaches to MSY are an inadequate foundation for optimum yield. Surplus production models are fit to catch and effort data under the assumption that the rate of expenditure of effort is proportional to fishing mortality rate. Often, this assumption is not valid. Furthermore, the most common method of fitting surplus production models to data may falsely indicate that the model satisfactorily describes the fishery. Because of the random fluctuations in productivity of fisheries, the fishing mortality rate corresponding to MSY will produce an average yield less than MSY. Maximizing yield per recruit may lead to a severe depletion of spawning stock size and recruitment failure. For multispecies fisheries, independent management of several species aimed at achieving MSY for each may be s...