Identification traits for the grenadiers Macrourus caml and M. whitsoni for onboard observer's use with preliminary attempt in Subarea 88.3

We investigated molecular and morphological traits of 338 individuals of macrourids collected in Subareas 88.1 and 88.3 between 2021 and 2022. Samples were classified into Macrourus caml and Macrourus whitsoni based on the morphological identification keys such as the number of pelvic fin rays (PF) and the row of lower jaw teeth (LJT). Four individuals had confusing morphological traits, for example, PF and LJT were overlapping between the two species. Subsequently, we obtained and analyzed 509 bp of mtDNA COI sequences of 49 individuals including 4 confusing individuals. Our results suggest that the number of PF and LJT should be investigated together in order to identify the two species exactly. When onboard observers attempted preliminary identification of grenadiers based on two presented morphological traits, there were 87 individuals identified as M. caml and 13individuals as M. whitsoni. However, the secondary morphological identification conducted in the laboratory showed a difference, with 99 individuals identified as M. caml and only 1 individual as M. whitsoni. This difference may be attributed to the overwhelming dominance of M. caml in Subarea 88.3, making it challenging for observers to differentiate between the two species.