The population structure of North Pacific pollock is complex and scientific understanding is evolving. In Russia, West Bering Sea Karaginsky, West Bering Sea Chukotsky, Sea of Okhotsk, and Sea of Japan pollock stocks are considered reproductively isolated from one another, albeit with some inter-migration between them, and are addressed separately from one another by the Russian authorities for purposes of stock assessment (Kotenev and Glubokov 2007); (Federal Fisheries Agency, Kamchatka Branch 2020). Russian authorities also recognize that there are fish that originate in the Japanese EEZ harvested in Russian waters (i.e., a separate Japanese Pacific stock) (Ovsyannikova 2012).  

Within these groupings, the degree of differentiation among various populations is nuanced. Complications in elucidating pollock population structure include life histories that entail different habitats for spawning, overwintering, and feeding; larval drift from one region to another; and different population dynamics at low and high abundance (Kotenev and Glubokov 2007); (Grant et al. 2010).

Within the broader Sea of Okhotsk region, the fisheries management sub-areas of North Okhotsk, West Kamchatka, and Kamchatka-Kuril--sub-areas 61.05.1, 61.05.2 and 61.05.4 shown in this map include most of the main spawning and over-wintering habitat of Sea of Okhotsk pollock and are considered in the Sea of Okhotsk profile. A smaller concentration of spawners is located off the eastern coast of Sakhalin, and is treated by fishery managers as a separate stock with low interconnectivity with the population located in the three aforementioned sub-areas of the northern Sea of Okhotsk (Lloyd’s Register 2021). The East Sakhalin sub-area is the subject of this profile.