The west coast of Sweden has two large sea basins, the Kattegat in the south and the Skagerrak in the north. Both together are commonly referred to as “the Western Sea”. It stretches out towards Denmark and Norway and out to the North Sea. It is teeming with life. From fish, crabs and clams to starfish, sea anemones and seals.
The Western sea contains the two smaller seas Skagerrak and Kattegat. The currents in these waters interact and contribute to the rich life beneath the surface. For example, the current carry flat fish larvae from the North Sea, along the coast of Denmark and eventually into the protected bays on the Swedish west coast, where the larvae grow into adult flatfish.
Skagerrak is the water basin containing the most species in Sweden. About 1,500 species of animals and plants live here, thanks to the high salinity – around 30 per thousand or more. The open sea of Skagerrak extents into the Bohuslän archipelago, to the bathing bays and the deep fjords, like the Gullmar fjord.
In the Kattegat the salinity is drastically lower. It reduces gradually as you travel south along the Swedish west coast, as the inflow from streams and rivers increase. In the Öresund area, the salinity is only around 15 per thousand. Therefore, the species richness is only about half as large as in the Skagerrak. About 800 plants and animals live here.