The Arctic Cod (Boreogadus saida) is a small, schooling fish overwhelmingly abundant across the frigid waters of the circumpolar Arctic. This species is unique for its ability to thrive in sub-zero temperatures due to a specialized antifreeze protein in its blood. The sheer mass of the population makes it a central component of the northern marine environment, acting as a primary energy channel moving fuel from the base of the food web to top predators.
Marine Mammals That Rely on Arctic Cod
The Arctic Cod is a fundamental food source for the region’s marine mammals, providing the high-fat content necessary to sustain life in the extreme cold. Ringed Seals, the most numerous marine mammal in the North, actively pursue the cod and rely on them as preferred prey. This high-energy meal is important during the dark winter months when other food sources are scarce.
Larger seals, such as the Bearded Seal, also consume Arctic Cod when schools are concentrated. Among the toothed whales, both the Beluga and the Narwhal depend heavily on this small fish. For Narwhals, Arctic Cod can constitute a main part of their diet, particularly during the summer when they feed in the upper water column.
The schools of Arctic Cod represent a reliable, concentrated source of calories that allows these mammals to build and maintain the thick blubber layers needed for insulation. A decline in the cod population would immediately diminish the energy reserves for many seal and whale species.
Avian and Fish Predators
A variety of seabirds and larger fish consume Arctic Cod, targeting different life stages. Seabirds like the Thick-billed Murre, Black-legged Kittiwake, and Northern Fulmar dive to capture the cod, often focusing on younger, smaller individuals. These birds tend to hunt age-1 cod, which are typically between 5.7 and 16.1 centimeters long, concentrating their efforts near the surface or the marginal ice zone.
Larger predatory fish also consume the Arctic Cod deeper in the water column. Native species such as Arctic Char and the deep-dwelling Greenland Halibut prey on the cod. Warming ocean temperatures are allowing the larger Atlantic Cod to migrate further north, introducing an additional, substantial predator that feeds on Boreogadus saida.
The Arctic Cod’s Pivotal Role in the Ecosystem
The Arctic Cod serves as the primary energy conduit between the lowest and highest trophic levels in the Arctic Ocean. The cod feeds primarily on zooplankton, such as copepods and amphipods, which are rich in fatty acids. By consuming these tiny organisms, the cod transforms the energy from the plankton into a larger, energy-dense food package.
It is estimated that this species funnels over 70% of the energy from zooplankton up to the marine mammals and seabirds. This efficient energy transfer has earned the fish the nickname of a “fat factory” within the ecosystem. The high lipid concentrations it accumulates make it a valuable food source for its predators.
Any significant change in the cod population has a rapid, cascading effect throughout the entire Arctic food web. If the cod’s numbers drop, top predators lose their most energy-rich and abundant prey, leading to widespread nutritional stress. The health and stability of the entire Arctic ecosystem are intrinsically linked to the fate of the Arctic Cod.