Öresjö

Öresjö, located in the municipalities of Trollhättan, Lilla Edet and Vänersborg, is an oligotrophic lake of 1093 ha (approx. 11km²) with a greatest depth of 33 metres. Despite the lake being in an area affected by acidification, the water quality is good, with a pH of around 7.0. The lake is regulated, with a difference of 1m between the impoundment and drawdown limits. Öresjö is part of the Bäveån catchment area, which is a protected area for Uddevalla's water supply (Köperödssjöarnas water protection area). The lake's eastern arm is dominated by holiday housing. The surroundings in the other parts are mainly characterised by coniferous forest and rocky and moraine shores. In the central parts of the lake there are several both larger and smaller islands and skerries. Depth varies greatly, from 20-30 m in the central parts to shallow sections in small bays, particularly in the south-west and north. Öresjö has a stable stock primarily of perch and pike. During a test fishing survey in 2005, 9 fish species were caught and reproduction was found to be relatively good. Fishing is easiest from a boat. Apart from the area around the bathing sites in the eastern part, the other parts are relatively difficult to access for fishing from shore. Öresjö is unique in that such a large lake, so far south, holds a good stock of noble crayfish and that the lake has not been affected by crayfish plague. Since 2010, the noble crayfish has been classified as critically endangered in the national Red List of threatened animal species. On 2015-06-11, the County Administrative Board decided that Öresjö shall constitute a protected area for noble crayfish. Boats Due to the risk of spreading crayfish plague, great caution must be observed before boats may be launched. Boats, canoes etc. used in other waters during the last two weeks must be disinfected before launching. As the lake is also part of a water protection area, two-stroke engines that do not meet new emission requirements are prohibited. A launch ramp is available in Munkeboviken at the lake's eastern arm. Permits can be purchased from Turistbyrån Drottningtorget Trollhättan In the area there is one or more waters for catch-and-release, i.e. the fish are carefully released after capture. Free fishing for children and young people up to and including the age of 15. Trollhättan-Öresjö Fiskevårdsområdesförening manages fishing in Öresjö and the two smaller lakes Stuvvikesjön and Gropsjön at Öresjö's south-western tip. The association has approx. 105 members. The association has previously carried out several stockings of char, but no reproduction has been established. More recently, the association's activities have mainly focused on protecting and developing the lake's stock of noble crayfish. A management area for noble crayfish was formed during 2012 and in 2015 the County Administrative Board decided that Öresjö shall constitute a protected area for noble crayfish. Unfortunately, the lake was affected by crayfish plague in autumn 2021. The association plans to reintroduce noble crayfish when the lake has been declared plague-free.