Overfishing does not only deplete the specific fish caught, it also changes the sea’s food web structures. Predators, such as seals and seabirds are affected negatively when the fish they normally eat decrease, while prey fish and organisms increase and take over as their natural predators like cod in the Baltic Sea disappear.
Fishing in the Baltic Sea is regulated by the European Common Fisheries Policy. Specific quotas are set for each of the most important commercial species. Because the quotas historically have been higher than the reproductive capacity of the ecosystem, they have led to decreased or depleted fish stocks. Overfishing also occurs through by-catch and illegal fishing.
The diagram below showcases the complexity of the Baltic Sea ecosystem where both the activities out at sea as well as on land have an impact on the well being of fish stocks and overall marine ecosystem of the Baltic Sea.