
The Baltic Sea is the world’s largest coherent brackish sea area. Its salinity is much lower compared to ‘true’ marine seas like the North Sea. Although these are unfavourable conditions for marine fish species, over thousands of years their populations have adapted to the specific hydrographic conditions in the different basins of the Baltic Sea. Marine fish species like cod, herring and sprat form the basis of productive fisheries. Flatfish like plaice, flounder, dab and turbot are commercially fished, too.