The Casal2 stock assessment software package is being developed to implement an updated generalised age-structured population model that allows more flexibility in specifying the population dynamics, parameter estimation, and model outputs than CASAL.
The package is approaching a development point where it can be considered for use by CCAMLR for tag-based toothfish assessments. Casal2 models can be built with user-defined categories such as area, sex, and maturity, and has been constructed to allow for alternative parameterisations of processes and observations to be compared between models. The structural elements of a model in Casal2 are generic and user defined. Casal2 models can be used for a single population with a single anthropogenic event (i.e., a single fishery), or for multiple species and populations, areas, and/or anthropogenic or exploitation methods.
Casal2 is open-source and is available at https://github.com/NIWAFisheriesModelling/Casal2. Comparisons of CASAL and Casal2 in a few stock assessments for New Zealand species show that they provide the same results for estimation of key productivity parameter, but more validation is required.
A Casal2 workshop will be held later in 2021 for scientists who wish to engage in the development and testing of Casal2, and we invite Members to participate in this workshop and in an e-group to develop test cases for presentation at WG-SAM in 2022.