Multi-fleet stock assessment modelling with the Grym

Grym is an implementation of the Generalized Yield Model in R that provides greater transparency and extensibility (Maschette et al., 2020, Wotherspoon & Maschette, 2020). This paper describes an extension of the Grym to permit multiple fleets within a season, allowing the Grym to model more complex fishery behavior and evolving fisheries practices. Results from the expansion are compared with existing analyses from the Grym. The model can include vessels using different gear types (e.g. trawl and longline) or identical selectivity. An example is presented for Patagonian toothfish.