Abstract <p>This paper reports the results of a study on the geographic, bathymetric, and temperature distribution of the southern horned poacher (<i>Hypsagonus corniger</i>) in the northern Sea of Japan and near the eastern coast of South Korea. The depth and temperature ranges at which this species was found proved wider than earlier assumed. Seasonal bathymetric migrations of the species and its concentration sites in different areas of the Sea of Japan were considered. Long-term biomass changes were assessed. The theory was proposed in relation to the fact that the horned poacher developed as an independent species relatively recently, in the Sea of Japan separation period.</p>