Fish in a changing climate - can cod cope?

Last changed: 24 September 2021
Cod on underwater meadow

Cod is a keystone species in marine ecosystems. It shapes the conditions for a large number of other species in the sea and is also of great importance both economically and culturally. However, the Swedish Atlantic cod stocks are on the verge of collapse with serious population declines observed in the Baltic Sea and on the Swedish west coast. Will the already weakened stocks meet another challenge; climate change?

Research based on the latest climate models shows that the temperature will rise and lead to local heat waves. Ocean acidification will increase, and salinity will reduce in the Baltic Sea and part of the west coast. Together, these climate effects will dramatically alter the marine environment around Sweden.

Climate effects cause physiological stress

Each of these changes can cause physiological stress in marine organisms. In order to better understand the anticipated fate of cod in a changing climate, this project aims to investigate how Atlantic cod (Gadus morhua) from coastal populations in the Baltic Sea and the North Sea respond to the cumulative effects of climate change factors such as reduced salinity (freshening), reduced pH (ocean acidification) and increased temperature (warming events).

The project is based on experimental studies where juvenile cod from the Baltic Sea and the North Sea, respectively, are kept in aquariums that simulate the various changes. The sensitivity of cod is measured by physiological variables

Room with experimental tanks
The experiment room at Kristineberg research center in Fiskebäckskil. The experiment is a four week exposure period under which the cod is exposed to different global climate change factors. Photo: Diana Hammar Perry
Tank with cables
The physiological stress response from cod will be evaluated using respirometry and oxidative stress analyses. The picture shows the respirometer set-up. DNA samples will be collected to determine the cod populations. Photo: Diana Hammar Perry
Cod in experiment
Cod in respirometer tank. The project studies juvenile cod from west coast and Baltic cod. In the autumn of 2020, experiments were carried out on cod from the west coast and in the autumn of 2021, the experiments will be repeated with Baltic cod. Photo: Diana Hammar Perry.

Food and climate

Will future generations be able to eat cod? Here, Diana Hammar Perrytells about how climate change affects cod and about the project where she investigates how cod reacts to physiological stress.

Knowledge for climate-adapted management

The project results will provide detailed knowledge of the sensitivity of different populations of Atlantic cod and an indication of how they might respond to future climate change. This knowledge may, together with spatial projections of climate change effects, be a crucial means of climate readying the management strategies for cod in the future to ensure that the environment, anglers and the fishing industry can all continue to enjoy the fish for generations to come.


The research team consists of Diana Hammar Perry (SLU Aqua), Håkan Wennhage (SLU Aqua), Filip Svensson (SLU Aqua), Martin Gullström (Södertörn University), Albin Gräns (SLU) and Michael Axelsson (University of Gothenburg)


The project "Sensitivity of Swedish cod populations to global climate change stressors " is funded by the Swedish Environmental Protection Agency and is ongoing 2020-2023. 


Diana Hammar Perry, Environmental Monitoring and Assessment Analyst
Department of Aquatic Resources,  SLU, +46(0)10-478 40 97