Preliminary Observations on Morphological Distinctions Among Eight Crocodile Icefishes (family Channichthyidae) Collected in the Antarctic Krill Fishery

This report presents preliminary observations on morphological distinctions among eight species of the family Channichthyidae (icefishes), collected as bycatch during commercial krill trawl operations in Subareas 48.1 and 48.2 between 2023 and 2024. The specimens, covering various ontogenetic stages, were collected by scientific observers aboard Korean krill trawlers, and provided for this study. This study aims to present the molecular phylogenetic relationships of these eight crocodile icefish species and to describe their morphological traits in relation to growth. A neighbor-joining tree based on mitochondrial COI sequences supported both the monophyly and morphological differentiation of each species. Key external features—such as pelvic fin length and coloration, lateral line patterns, gill pigmentation, and body proportions—were analyzed to distinguish among species. These morphological indicators provide valuable information to improve bycatch species identification protocols and enhance understanding of the spatial and developmental distribution of icefishes in the region.