Walleye Pollock

Walleye pollock is a schooling fish in the cod family found throughout the North Pacific, with especially large populations in the Bering Sea and Gulf of Alaska. It is one of the most abundant fish species in the North Pacific and forms a major component of the region's mid-water and demersal fish communities. Walleye pollock has a slender, silvery body with a distinctly protruding lower jaw and a small chin barbel, and it typically forms enormous schools that move between deeper daytime depths and shallower waters at night. The species was formerly classified in the genus Theragra before being reclassified into Gadus, the same genus as Atlantic and Pacific cod.

Walleye pollock has a slim, elongated body typical of active schooling relatives of cod.

• Silvery sides with dark speckled or mottled patterning along the upper back
• Protruding lower jaw, giving a slight underbite
• Small, thin chin barbel, less obvious than in true cod
• Three dorsal fins and two anal fins
• Forked tail fin, more pronounced than in bottom-dwelling relatives like cusk or hake

Its slender, silvery, schooling profile with a forked tail sets walleye pollock apart from bottom-hugging relatives such as cusk and hake, while its small barbel and speckled back distinguish it from pollack, which lacks a barbel entirely.

Walleye pollock is distributed across the North Pacific, with major concentrations in the Bering Sea, Gulf of Alaska, and Sea of Okhotsk, extending south to Japan and North Korea. It occupies a semi-pelagic niche, forming large schools that range from near-surface waters to depths of several hundred meters, often moving vertically between deep daytime aggregations and shallower nighttime feeding depths. Walleye pollock tolerate cold sub-arctic waters and are closely tied to the productive continental shelf ecosystems of the Bering Sea. Juveniles often use shallower coastal and shelf waters, while larger adults range more broadly across open shelf and slope habitat.

Walleye pollock are highly gregarious, forming some of the largest fish schools in the North Pacific, a behavior that helps them exploit dense concentrations of plankton and small prey while providing some protection from predators. They undertake pronounced vertical migrations, moving toward the surface at night to feed on zooplankton and small fish and retreating to deeper water during the day. Spawning occurs in large aggregations, primarily in late winter and spring, releasing enormous numbers of pelagic eggs that drift and hatch in open water. As one of the most abundant fish in the North Pacific, walleye pollock is a critical prey base for seabirds, marine mammals, and larger predatory fish.