Själsöån, Naturreservat

Själsöån flows into the sea immediately south of Själsö fishing village. In the river you can see spawning sea trout and also river lamprey.
Fish conservation efforts and research into the ecology of sea trout have been carried out in the Själsö River for a long time. An excellent way to study the spawning sea trout is to do so from the footbridge that has been built along the river.

During the spawning season in late fall, sea trout migrate from the sea into the freshwater streams. Spawning takes place on shallow gravel or rocky bottoms. A female trout can produce tens of thousands of eggs, which hatch the following spring. After hatching, the fry normally remain in their natal stream until they are one to two years old. However, the drying up of Gotland's streams during the summer means that many trout are forced into the sea during their first year of life. The return to the streams for reproduction usually takes place after at least two years in the sea, and sea trout can spawn several times during their lifetime.

The river also contains reproducing river lamprey, an eel-like fish belonging to the class
of round gobies. Its life cycle is complicated but ends with a spawning migration to streams with suitable gravel bottoms for reproduction. Spawning occurs in late spring, often in the same environment as sea trout.