Review of grenadier species-level data as longline bycatch in Subarea 48.6

In CCAMLR Subarea 48.6, research longline fishing operations that target Antarctic toothfish (Dissostichus mawsoni) have operated since 2012. Because grenadiers (Macrourus spp.), the main bycatch taxa in this fishery, include multiple species with different life history characteristics and ecological traits, species-specific assessment is desirable to understand the structure of, and potential fisheries impact on, the Antarctic ecosystem. In this study, we examined the reports of grenadier bycatch in the observer data for Subarea 48.6, to provide a basis for species-specific modeling. While the observer data contains a lot of potentially useful information to assist in species identification of Macrourus when linked to the C2 data, we detect a few caveats, especially in applying the approach of Moore et al. (2023). It is required to further scrutinize the data to find an approach toward species-specific assessment of grenadier bycatch in the area.