According to scientists at the International Council for the Exploration of the Seas (ICES), the eastern Baltic cod stock has increased since 2005 and is now higher than ever during the last decade. Researchers at Stockholm University analyzed whether this increase is a result of management actions reducing the fishing pressure or improved environmental conditions resulting in higher reproduction.

Model simulations show that neither reduced catches alone, nor higher reproduction, could explain the increase. Each factor only explained 25% of the total increase. Synergies between both factors were necessary for the current increase in the Baltic Sea cod stock.
– This analysis clearly illustrates the importance of management actions but it also underlines the non-linear dynamics in nature and the challenges involved in ecosystem management, says Henrik Österblom at Baltic Nest Institute and one of the authors behind the study.

Does this mean that the Baltic cod stock is safe now?
– A similar increase of the cod stock in the early 1990’s was rapidly nullified by unsustainable catches. But we are, now in a window of opportunity to re-build the cod stock. If only the management plan decided last year is followed and illegal catches are controlled, the future of the Baltic cod looks better than it has for a long time, according to Olle Hjerne, marine ecologist at Stockholm University.

What will happen if the environmental conditions change?
– As climate change continues, environmental conditions for cod will be affected. Research on cod in other seas has underlined the importance of high stock levels for its capacity to cope with environmental change. Climate change will thus underline the importance of adaptive management, according to Thorsten Blenckner, Baltic Nest Institute.

The study is a work in progress at Stockholm University (the Department of Systems Ecology, the Baltic Nest Institute at Stockholm Resilience Centre).

About the Department of Systems Ecology
Research and teaching in the Department of Systems Ecology at Stockholm University focuses on the study of ecosystems and on sustainable use of natural resources. The Department of Systems Ecology studies both basic and applied ecological problems, with an emphasis on coastal and marine ecosystems and coupled social-ecological systems.

About Baltic Nest Institute
The Baltic Nest Institute hosts and develops Nest – a science based decision support system of the Baltic Sea. By modeling the entire drainage area as well the sea, Nest is a novel tool for implementing an ecosystem approach in a large marine ecosystem.

Baltic Nest Institute represents a strategic alliance between Stockholm University, Swedish Environmental Protection Agency, National Environmental Research Institute (NERI), University of Aarhus, Danish Meteorological Institute and National Institute of Aquatic Resources at the Technical University of Denmark (DTU-Aqua), Danish Technical University.

About Stockholm Resilience Centre
Stockholm Resilience Centre advances transdisciplinary research for governance of social-ecological systems with a special emphasis on resilience – the ability to deal with change and continue to develop.

The centre is a collaboration between Stockholm University,Stockholm Environment Institute and the Beijer Institute of Ecological Economics at the Royal Swedish Academy of Sciences. The centre is funded by the Foundation for Strategic Environmental Research, Mistra.

For more information, please contact:
Dr. Olle Hjerne: or +47 730 979 090
Dr. Henrik Österblom: +46 73 707 88 16
Dr. Thorsten Blenckner: or +46 73 707 85 79
Press contact Ellika Hermansson Török: +46 73 707 85 47,