Competition for Gear in a Multiple-Species Fishery

Abstract

The catch-per-unit-of-effort (CPUE) for one species may affect the CPUE of another species in a multiple-species fishery. This effect is studied by means of a simple stochastic model. The model provides a “competition free” CPUE which is never less than the CPUE obtained under competition, is strongly dependent on the empty space on or in the gear, and varies as a function of the proportion of each species. The multinomial structure of the model enabled the derivation of maximum-likelihood estimators of its parameters.Estimates of the large sample sampling variances and covariance of the parameters are also provided. Application of concepts of the model to other fishery problems is discussed and it is noted that the model also provides a maximum-likelihood estimate for the well-known yield equation.