Alaska pollock

The Alaska pollock, scientifically known as Gadus chalcogrammus, is a highly significant marine fish species. It belongs to the cod genus, Gadus, and the family Gadidae. These fish are semi-pelagic, meaning they live in the water column rather than staying strictly on the ocean floor. They are schooling fish, which means they travel together in large, organized groups. The Alaska pollock is widely distributed across the North Pacific Ocean. The largest concentrations of these fish are located in the eastern Bering Sea.

Understanding the biological classification of the Alaska pollock has required significant scientific research. In 1956, the species was placed in its own genus, Theragra, and named Theragra chalcogramma. However, research conducted in 2008 revealed a close genetic relationship to the Atlantic cod. This discovery suggested the fish should return to the Gadus genus. In 2014, the U.S. Food and Drug Administration officially changed the name back to Gadus chalcogrammus. Major scientific registries, such as the World Registry of Marine Species, have since adopted this name. While common names like "walleye pollock" are still used in trade, scientists consider them somewhat misleading.

The ecology of the Alaska pollock is deeply connected to the health of the Bering Sea. These fish have speckled coloring, which provides camouflage against sandy ocean floors. This helps them avoid being seen by predators. The species is relatively fast-growing and has a short lifespan. Interestingly, the population size is affected by weather patterns. When stormy summers occur, they stir up nutrients in the water. These nutrients promote the growth of phytoplankton, which is a tiny plant-like organism. A higher amount of phytoplankton leads to better survival rates for pollock hatchlings.

Pollock foraging behavior changes significantly based on the age of the fish. Young pollock are divided into two groups based on their length. Fish smaller than 60mm mainly eat copepods, which are tiny crustaceans. Those larger than 60mm eat copepods but also forage for krill. This difference means that a lack of food affects smaller fish more heavily. Seasonality also plays a role in how they hunt. During winter, food is scarce and hunting is risky due to predators. Large young pollock can store more energy and do not need to hunt as much in winter. Smaller fish lack this storage capacity and must continue foraging, increasing their danger.

These fish also participate in diel vertical migration to find food. This is a process where fish move up and down in the water column. While they move vertically during the day, their average depth changes with the seasons. This movement is not driven by light or temperature, but by the movement of their food. In August, food is abundant near the surface, so pollock stay in shallower depths. In November, they move to deeper waters to follow their planktonic food source.

History shows a complex relationship between the Alaska pollock and the Norwegian pollock. In 1956, zoologist Einar Koefoed identified a rare fish in Norway as a separate species, Theragra finnmarchica. He based this on morphological differences, or physical appearances, from specimens caught in 1932. However, modern genetic analysis has changed this view. DNA sequencing of specimens showed no significant genetic differences between the two. Researchers concluded that the Norway pollock is actually the same species as the Alaska pollock. This makes the Norway pollock a junior synonym of Gadus chalcogrammus.

The Alaska pollock is a massive component of the global fishing industry. It is the second most important fish species in the world by total catch. In the United States, pollock landings are the largest of any single fish species. Between 1979 and 2022, the average annual catch in the eastern Bering Sea was 1.26 million metric tons. U.S. fisheries maintain a consistent average of about 1.3 million tons per year. Most of this, about 92 percent, comes from the Bering Sea. To prevent overfishing, the Alaska Fisheries Science Center conducts stock assessments to set yearly quotas.

This fish is a primary ingredient in many different food products. It has a mild taste, white color, and low oil content compared to other cod. High-quality fillets are often used for breaded fish products in Europe and North America. The fish is also the main material for surimi, which is used to make imitation crabmeat. Surimi can be found in many forms, such as chunks, legs, flakes, salads, or shreds. In Korea, the Alaska pollock is considered the national fish. In Russia, the roe, or fish eggs, is often sold as a canned spread.