Integrating otolith shape and niche model to infer population structure of mackerel icefish (Champsocephalus gunnari) between South Orkney Islands shelf and South Georgia shelf, Antarctic

As an important species in the Southern Ocean, the mackerel icefish (Champsocephalus gunnari) is not only a major food source for a wide range of top predators, but also a predominant consumer of a key species, Antarctic krill (Euphausia superba), in the Southern Ocean ecosystem. In the Scotia Sea, this species is commercially harvested at South Georgia. However, the studies on the population structure of this species are inconclusive. Combining Trait Probability Density and Ecological Niche Modeling analyses on otolith shape, this study investigated the diffidence in populations of C. gunnari between the South Orkney Islands and South Georgia. Significant differences were identified in the otolith shape characteristics and ecological niches of fish from these two regions, with otolith roundness and aspect ratio likely being the primary factors responsible for these differences. The results of these analyses indicate that populations are separated between the two regions. This multi-dimensional approach offers new insights for otolith study and valuable data for understanding the ecological niche and population structure of fish species, thereby enhancing our ability to effectively manage and conserve C. gunnari populations.