Population genetic structure and spring−summer spatial distribution of common minke whales (Balaenoptera acutorostrata) in feeding grounds and migratory corridors of the western North Pacific

Information on population genetic structure, movement, and distribution is fundamental for effective management of marine species. In the western North Pacific, the common minke whale faces both bycatch and commercial whaling, the latter having resumed in Japanese waters in 2019. In this study, we refined the population genetic structure and spring–summer spatial distribution of this species using 6196 genetic samples collected in feeding grounds and migratory corridors during 1994–2024. Genetic analyses of the mitochondrial DNA control region and 16 microsatellite loci confirmed the previously recognized Sea of Japan–Yellow Sea–East China Sea (J) and Sea of Okhotsk–West Pacific (O) stocks, which overlapped along the Pacific and Sea of Okhotsk coasts of Japan. Spatial analyses identified fine-scale differences in distribution by stock, sex, and sexual maturity class. In both stocks, mature whales were found farther offshore than immature whales. In the J stock, both sexes were concentrated in coastal waters, whereas the O stock exhibited a broader distribution that varied by sex and maturity class, with mature males being found more frequently offshore. These findings have important implications for stock assessment and management and may inform future management strategies for western North Pacific common minke whales.