Alaska Pollock

Alaska Pollock (Gadus chalcogrammus), also called Walleye Pollock, is a schooling member of the cod family Gadidae found throughout the cold North Pacific, with the largest populations in the Bering Sea and Gulf of Alaska. It is one of the most abundant fish species in the world by biomass and supports one of the largest single-species commercial fisheries globally, managed under close scientific monitoring in U.S. and Russian waters. Genetically and taxonomically very close to Atlantic Cod, it was formerly classified in the genus Theragra before being reassigned to Gadus. Alaska Pollock plays a central ecological role as both predator and prey within North Pacific marine food webs.

Alaska Pollock shares the general cod body plan but has features suited to its more schooling, midwater lifestyle.

• Jaw: lower jaw projects slightly beyond the upper jaw
• Barbel: present but small and inconspicuous compared to Atlantic or Pacific Cod
• Color: olive-brown to golden above with irregular dark speckling, silvery sides, pale belly
• Fins: three dorsal fins, two anal fins, slightly forked tail
• Size: typically 30-60 cm, smaller and slimmer than Pacific Cod Its smaller size, slimmer build, and less prominent barbel help distinguish Alaska Pollock from the more heavy-bodied Pacific Cod sharing its range.

Alaska Pollock is found throughout the cold North Pacific, with the greatest abundance in the Bering Sea, Gulf of Alaska, and Sea of Okhotsk, extending into the Sea of Japan. It occupies a wide depth range, from near-surface waters at night to several hundred meters during the day, reflecting a strong daily vertical migration pattern tied to feeding. Pollock favor open continental shelf and slope waters rather than rocky reef structure, forming large aggregations over relatively featureless bottom or in open midwater zones. The species tolerates a broad range of cold temperatures typical of subarctic Pacific waters and shows strong seasonal movement between spawning and feeding grounds.

Alaska Pollock is a highly schooling species, often forming enormous aggregations that undertake daily vertical migrations, moving toward the surface at night to feed on plankton and small fish and descending to deeper water during the day to avoid predators. It feeds opportunistically on krill, copepods, and small fish, including at times its own juveniles. Spawning occurs in late winter to spring at well-documented aggregation sites, particularly in the Bering Sea, where enormous numbers of individuals gather to release pelagic eggs. Because of its huge numbers and schooling behavior, Alaska Pollock serves as a critical prey resource for marine mammals, seabirds, and larger fish, making it a keystone species in North Pacific ecosystems.