Climate change threatens Arctic polar cod stocks

Arctic cod (Boreogadus saida), also known as polar cod, play a pivotal role in Arctic marine ecosystems. They are a key food source for marine mammals, seabirds and other fish species harvested by Inuit as well as commercial fisheries.

In the new study an international consortium of 43 scientists from 26 international institutions reviewed 395 scientific papers on Arctic cod published between 1954 and this year. The study consolidates existing research and presents a new evaluation of the current and future impact of climate change on Arctic cod populations and their ecosystems across all Arctic regions.

“Our findings emphasize the urgent need for action to mitigate climate change impacts on Arctic cod populations. These changes are not only affecting the most abundant fish of the Arctic, but also disrupting the delicate balance of the entire Arctic ecosystem,” said Dr. Maxime Geoffroy, research scientist with the Fisheries and Marine Institute of Memorial University of Newfoundland and lead author of the study.

An important part of the study was the authors' expert assessment of the future prospects for Arctic cod through the middle of this century, coordinated by Dr Hauke Flores, marine biologist at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). "Bringing together so many perspectives in a rigorous assessment of the impact of the climate crisis and other stressors on Arctic cod was quite a challenge," says Flores. "But there were some clear results. Sea-ice decline and ocean warming are the biggest threats to the future of Arctic cod; the youngest life stages are most vulnerable to the effects of the human-induced climate crisis." He adds: "Sea ice is very important to this fish. It provides protection from predators for eggs and up to 2-years old fish, and provides unique prey even in winter. The rapid transformation and loss of this habitat is therefore already having a significant impact on Arctic cod.”

The study highlights several key findings:

Habitat loss: Rising temperatures and shrinking sea ice pose a significant threat to the Arctic cod’s habitat, especially for the eggs and larvae. These changes disrupt the species’ reproductive cycles, survival, predation risks, growth, distribution and feeding ability.

Altered food availability: Climate change results in smaller and leaner zooplankton prey available for Arctic cod larvae and juveniles. This can lead to reduced growth rates and higher larval mortality and, ultimately, reduced numbers of Arctic cod.

Increased predation and competition: As sea ice retreats, Arctic cod face increased exposure to predators and competitors from the North Atlantic and northern Pacific oceans. New species of seabirds and larger fish species are also expanding their range into previously inaccessible areas, and this heightened predation and competitive pressure could have cascading effects throughout the ecosystem.

Increased risks from oil and gas activities: The main risks from human activities in the Arctic are related to potential oil spills at the surface. Arctic cod larvae and juveniles exposed to crude oil experience reduced survival and growth as well as greater deformities.