Simulation experiments and CCAMLR yield estimates using CASAL

This paper describes an approach, using CASAL, to undertake operating model/estimation model experiments for Dissostichus spp., and methods for calculating CCAMLR yields using CASAL. We present an example model for the fictitious fishery on a fictitious species Dissostichus spurious (Everson, 2004) and investigate model performance from alternative types of observations. In general, most models were fitted with an expected percent root mean squared error (%RMSE) of less than 20%. The inclusion of additional data (i.e., more observation types) assisted in providing better estimates.
Further research on the expected performance of integrated models is required that investigates a range of alternative “true” states with data that includes bias and variance in observations, as well as the robustness of the estimation model to alternative operating model assumptions. In addition, the expected uncertainty that may arise from an MCMC approach has not been considered here.
In general, operating/estimation modelling experiments provide a means of evaluating alternative approaches to the assessment of stocks, however it should be noted that simulation studies often under-estimate the uncertainty that would be found in a real assessment.