Appendix 5 . the Casa Length Structured Stock Assessment

The stock assessment model described here is based on Sullivan et al.’s (1990) CASA model. CASA is entirely length-based with population dynamic calculations in terms of the number of individuals in each length group during each year. Age is largely irrelevant in model calculations. Unlike many other length-based stock assessment approaches, CASA is a dynamic, non-equilibrium model based on a forward simulation approach. CASA incorporates a very wide range of data with parameter estimation based, in the broadest sense, on maximum likelihood. CASA can incorporate prior information about parameters such as survey catchability in a quasi-Bayesian fashion. The implementation described here was programmed in AD-Model Builder (Otter Research Ltd.).