Generalized Stock Reduction Analysis

In this paper we generalize Stock Reduction Analysis (SRA) so that the model now allows for growth in the fishable biomass, and variable recruitment to the fishable biomass. The application of R. B. Deriso's delay-difference equation to SRA allows for growth, and also provides justification for using a biomass based model. Variable recruitment is introduced into SRA using both a stock–recruitment relationship and exogenous variables. We present general methods for obtaining unique solutions to the SRA equations, and give a new method for calculating the equilibrium sustainable yield curve. By applying the generalized SRA model to Pacific ocean perch (Sebastes alutus) stocks in the Gulf of Alaska, we conclude that the sustainable yield from this stock is smaller than previously estimated.