River Ósá flows from Syðridalsvatn, which is a rather shallow lake 1.1 sq.km in size. Fish migrate into River Gilsá and River Fossá that run into the lake. Fishing is allowed in the lake during the rest period, if both slots/day parts have been purchased in the river. Arctic char are mainly caught there, but occasionally sea trout and salmon. The char in Ósá are from 1 – 2,5 lbs. The char fishing varies from year to year, as happens in rivers.