Fish in a changing climate – can cod cope?

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?

Cod on underwater meadow
Cod swimming through seagrass meadow. Photo. Diana Hammar Perry

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.

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.

Swedish University of Agricultural Sciences (SLU), 5 July 2021. Full article.

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