Öresjö, located 7 km west of Trollhättan, is a 1093 ha (approximately 11km²) large oligotrophic lake with a maximum depth of 33 meters.
The water quality is good with a pH around 7.0. Öresjö is part of Bäveån's catchment area, which is a protection area for the water supply of Uddevalla (Lake Köperödssjöarna).
The eastern branch of Öresjö is dominated by recreational housing. The surroundings in other parts are characterized mainly by pine forests and rocky and moraine beaches. In the central parts of the lake there are several larger and smaller islands and rocky islets. The depth varies from 20-30 m in the central parts to shallow coves especially in the southwest and north.
Öresjö has a stable population of mainly perch and pike.
Fishing is best done by boat. Apart from the area around the bathing areas in the eastern part, other parts are relatively difficult for fishing from land.
Considering the risk of spreading crayfish plague, great caution should be observed before launching boats. Boats, canoes etc. used in other waters during the last two weeks must be disinfected before launching. Since the lake is also part of a water protection area, two-stroke engines that do not comply with new emission requirements are not allowed.
Ramp for launching is in Munkeboviken at the eastern branch of the lake.
Fishing license can be purchased at Coop Konsum, Albertsvägen 77 Trollhättan and at SNÄJK, Karlslundsgatan 8 Vänersborg
Trollhättan-Öresjö Fiskevårdområdesförening manages fish in Öresjö and the two smaller lakes Stuvvikesjön and Gropsjön at Öresjös southwest tip. The association has about 105 members.