A General Approach for Making Short-Term Stochastic Projections from an Age-Structured Fisheries Assessment Model

A General Approach for Making Short-Term Stochastic Projections from an Age-Structured Fisheries Assessment Model

J. Brodziak, P. Rago, and R. Conser

A General Approach for Making Short-Term Stochastic Projections from an Age-Structured Fisheries Assessment ModelThis is part of Fishery Stock Assessment Models
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Catch-age analysis is a powerful tool for assessing the status of fisheries resources and catch-age analyses are routinely conducted for many commercially exploited fish stocks around the world. In this paper, we illustrate a general approach for making short-term stochastic projections from the ADAPT age structured assessment model. Our approach uses the standard statistical techniques of bootstrapping and Monte Carlo simulation to project performance measures such as landings, discards, spawning biomass, and recruitment under alternative management policies. The key idea is to propagate variability in estimates of initial stock size forward in stochastic projections of future possibilities. We use bootstrap replicates of current population size from an age-structured ADAPT model combined with a stochastic stock-recruitment relationship to simulate population trajectories through the projection horizon. The approach is illustrated for a commercially important New England groundfish, Georges Bank yellowtail flounder, Pleuronectes ferrugineus. Although hypothetical, this illustration provides some general insight for the rebuilding of the Georges Bank yellowtail flounder stock.

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