Fundamental Concepts of Fish Passage in Scandinavian Countries
Fish Passage Policy and Technology: Proceedings of a Symposium
American Fisheries Society
The earliest Scandinavian fishways were successfully excavated in cold rivers of Norway for Atlantic salmon (Salmo salar) and sea trout (S. trutta) for more than a hundred years ago. Latest statistics show that half of the 400 Norwegian fishways do not operate properly. On one hand the main reason for malfunction is lack of maintenance, yet, on the other hand lack of migrating fish or undesirable constructions. During the last decades mainly overflow fishways have been constructed there. In Sweden pool and weir fishways with orifices have traditionally been favoured. Fishway construction and fish planting side by side have proven successful in many rivers. In Finland planting of salmon and trout is usually carried out by hydropower companies, and hatcheries are often situated in large dammed rivers. On the pretext that wild fish bring diseases along, opposition to fishways has arisen. Up to now fishways, which usually are of the vertical slot type, have mostly been built in small watersheds and in many cases for freshwater species such as whitefish (Coregonus sp) and cyprinids.