Some 400 fish farms have been in operation in the 1990s. About two thirds of the fish farms are net cage installations located mostly in the marine environment. A minor part of the fish farms are land basin installations located in inland water bodies. In central and northern Finland there are over 200 fish farms and fishponds, in which about 300 tons of fish are produced yearly to be released in watercourses.
Fish farming is the third largest point source of nutrients after forest industry and communities.
Nutrient discharges from fish farming have caused eutrophication, which decreases the recreational value of ambient waters. Discharge of nutrients decreased by one quarter from 1990 to 1995. The main reason is the decrease in the specific discharge of nutrients, as better fish feeds were taken in use and feeding of fish was optimised.