A Length-Based Stock Assessment Method Utilizing a Generalized Delay-Difference Model

Abstract

We present a length-based stock assessment method based on a generalization of the delay-difference methods of Deriso. Data inputs to the model include the estimated weight of the catch, the estimated fishing effort, the estimated mean weight of the catch, and the estimated central moments of the length distribution of the catch. The model's performance is demonstrated by applying it to data from a simulated exploited fish population exhibiting biomass-dependent catchability which would cause conventional catch–effort models to seriously underestimate the extent of stock depletion. The model was generally able to detect the presence of the biomass-dependent catchability and to correctly estimate the optimal level of fishing effort.