The Baltic Sea is a unique but vulnerable environment with a small exchange of water, varying salinity, and large areas with dead zones. Cod is one of the Baltic Sea’s most important fish species, from an ecological, and previously economic perspective. Today, the Baltic Sea cod stocks are facing an acute situation due to decades of overfishing and unsustainable management.
Cod depend on a certain level of salinity and oxygen to be able to breed. The cod eggs need to float a bit above the bottom; however, the oxygen-depleted bottoms and the low salinity make the eggs sink to the bottom and die. Presently, there is only one place left in the southern Baltic Sea with the right conditions for successful cod reproduction.
In order for the stocks to recover in the Baltic Sea, a number of different measures are required, ranging from reducing the effects of eutrophication to continued regulations for cod fishing.
The project “ReCod – release of small cod in the Baltic Sea” aims to test whether it is possible to help cod pass the vulnerable egg stage and thus increase the number of small cod in the sea as a step in strengthening the fish population.
The project will conduct trials with cod larvae released to the sea and examine survival rate, their capacity to establish in new locations, and estimate at what cost it can be done. If the measure is successful, it could provide a template for future large-scale efforts to strengthen the stock.
The demonstration project is conducted at the research station Ar on Gotland – in the middle of the Baltic Sea. Baltic cod from the eastern stock will be continuously caught in order to later reproduce via natural spawning at the research station. The 5–6-day old cod larvae, i.e., fry (juveniles) that have made it past the egg stage, will then be released in the Baltic Sea at selected locations. Estimations show that about 1 – 1.5 million cod larvae per year will be released after breeding at the research station. Test fishing and scientific-based sampling will be conducted continuously to follow up the project results.
“ReCod – release of small cod in the Baltic Sea” is conducted by BalticWaters2030 in close cooperation with Uppsala University. In addition, there are a number of partners who contribute to the project in various ways: Leader Gute, Region Gotland, Swedish University of Agricultural Sciences and the Ulla and Curt Nicolin Foundation.
In total, close to SEK 50 million is invested in the project by the foundation and its partners. We will continuously evaluate new projects that can contribute to, and expand the work, at Ar.