Update on the VAST (vector autoregressive spatio-temporal) modelling of grenadier relative abundance in Subarea 48.6

In the present paper, we report progress since WG-FSA-2021 on the development of statistical modeling to estimate the abundance trends of grenadiers caught as bycatch in the longline fisheries in CCAMLR Subarea 48.6. This work relies on spatio-temporal delta generalized linear mixed models (GLMMs) implemented with R package “VAST”. We recommend that future studies keep improving the VAST modelling of grenadier relative abundance for Subarea 48.6. We particularly encourage the development of a single VAST model for Subarea 48.6 (instead of separate VAST models for the research blocks of Subarea 48.6), where the generation of indices of relative abundance will be possible for individual research blocks via the specification of “strata” within VAST. This endeavor will allow for the estimation of an index of relative abundance for research block 48.6_5.