Spawning. Pollock breeds in the cold period during the maximum cool water in the spawning grounds. Depending on the spawning time, populations differ in autumn (Korean Bay and Peter the Great Bay), winter (Hokkaido waters) and spring (the Sea of Okhotsk and the Bering Sea) spawning populations. The Pollock spawning period continues up to 6-7 months, and mass spawning, when most species complete reproduction, fits in 2-3 months.
In the Sea of Okhotsk, spawning period covers winter and spring seasons. Reproduction of Pollock in the western Bering Sea begins in March with the peak in May and is late as compared with the warmer south-eastern part of the Sea (from mid-February to April).
The main Pollock spawning grounds are located on the shelf or in the immediate vicinity, which prevents carrying out roe to deep-water areas with adverse conditions. In the Sea of Okhotsk, the most important role in Pollock reproduction belongs to the western Kamchatka spawning grounds including the southern part of the Shelikhov Gulf. The second in the spawning capacity is located south of the Tauiskaya Inlet.
The largest Pollock spawning grounds in the Bering Sea are located along the eastern Aleutian Islands and the Pribilof Islands. Pollock is propagated in the waters of the central and western part of the Aleutian Islands and also the Commander Islands. Reproduction of Pollock in the western part of the Sea takes place in the bays of Olyutorsky, Karaginsky and Ozerny. In certain periods large-scale spawning is noted in the bays of Eastern Kamchatka.
Pollock as a moderate cold-water specie mostly inhabits under low positive or close to zero negative temperatures, while the upper limit of its occurrence is 12-14°C. Under the water temperature below -1°C the development of roe is suspended, but it does not die, which enables Pollock to successfully reproduce in the areas with very harsh conditions. The size of the larvae, on average, is about 4 mm.
Pollock belongs to the fast-growing large fish with a relatively short life cycle; it reaches a maximum length of 93 cm (sporadically species of 1 meter long were observed) and a mass of 5 kg. Such species are rare; usually the maximum fish size in catches is 65-75 cm and weight of 2-3 kg. According to various sources Pollock lives up to 16-25 years. Pollock males, like many other fish, become mature earlier than females. Mass maturation occurs when the length is 34-38 cm, at the age of 4-5 years.
Natural mortality of Pollock varies by regions from 28% to 39% per year. The lowest indices are characteristic of the Sea of Japan Pollock, the maximum is for the Sea of Okhotsk and for the Bering Sea Pollock is 30 - 35%.
Food. Pollack belongs mainly to planktivorous fish, although fish fry can be essential in the diet including its own fry. Of benthic animals, the greatest importance in the diet belongs to shrimps. Pollock is a favorite food item of predatory fish such as halibut, cod, coal fish and grenadiers.
In the whole, Pollock in relation to environmental and nutrition factors is very plastic fish, therefore it has a high competitive ability in relation to other species, and that conditioned its dominant position in the ecosystems of the Far Eastern seas and determined the leading role in the world fisheries.