Development of the SCAS (Statistical-Catch-At-Size) Software

We have been developing Statistical-Catch-At-Size (SCAS) software since 2019 to improve our previous joint Age Structured Production Model (ASPM)/Statistical-Catch-At-Age (SCAA) software because of problems of uncertainties in the estimated CAA and usage of model-free selectivity. SCAS is the integrated age-structured stock assessment model based on size, and implemented by an AD Model Builder like Stock Synthesis 3 (SS3) and the ASPM/SCAA software. This SCAS software uses the simpler specifications than in SS3, i.e., the season aggregated model without spatial components, thus requires less numbers of inputs and parameters to be estimated. The SCAS software has two parts, [Part I] Point estimation and [Part II] Uncertainties and Risk assessments. In each Part, there are three menus, i.e., [Part I]: (a) Grid search, (b) Initial graphs, (c) Diagnoses (retrospective analyses) and [Part II]: (d) Markov Chain Monte Carlo (MCMC), (e) Diagnoses (hindcasting), and (f) Final graphs. As this software is based on the simpler specification than in SS3 and driven by menus thus no programming is required. Hence this software is suitable for those who wish to run the simpler integrated stock assessments. We completed two menus (a) and (b), while others are partially completed. In this document we describe (a) and (b) and plan to do the rest when we complete in 2022.