Shape and ontogenetic changes in otolith of the ocellated icefish (Chionodraco rastrospinosus) from the Bransfield Strait, Antarctic

Fish otolith shapes record ecological information of fish and are an important tool in taxonomic, phylogenetic, and dietary studies. Shape and ontogenetic variations in the otoliths of ocellated icefish (Chionodraco rastrospinosus) in the Bransfield Strait, northern Antarctic Peninsula, were analyzed. Ontogenetic changes in otolith morphology were evident. The size of the otoliths mainly grew along the antero-posterior axis. The rostrum and pararostrum developed more than the antirostrum and postrostrum. Otolith variation occurred mainly in the dorsal side compared to ventral side. A row of small holes in the central region of the medial side and an irregular protruded structure on both sides of them, were specific diagnostic characteristics of C. rastrospinosus otoliths compared to other species of Chionodraco. Based on hierarchical clustering analysis, four types of otolith shapes are clearly distinguished, corresponding to larval, juvenile, young, and adult stages of C. rastrospinosus. This work contributes to the understanding of the ecology of commercially important benthic fishes and provides key information for ecomorphology study and fishery management of this species. We suggest the effect of ontogeny needs to be considered when otolith shape data are used to study population structure and life history of this species.