When waterpower was used to run mills and sawmills, the river flow and the river width was only partially needed. In Finland, it was absolutely forbidden to block a river totally. Fish ascent was guaranteed by law. However, in the middle of the 19th century it became necessary to dam rivers across their whole width for waterpower production. The laws were changed in order to make the total damming easier. The first permits were granted already in 1868. Fishway obligations assigned to the owners of dams and water power stations to compensate for the impediment. Fishery administrators and officials in Finland were international as early as the 19th century, and collected knowledge of fishway construction from abroad. Based on this, Nordqvist (1892) wrote an advantageous and still current article on fishways and factors affecting their operation. Many of the early fishways did not, however, work properly, and gradually fishways were replaced by fish planting. An amendment to the waterlaw in 1987 no longer specifically mentioned the ascent of fish.
In recent years, fishway construction has started again in Finland on a new basis. This is partly due to the overall restoration of the river environment. Mainly, small fishways have been constructed, usually in small watersheds. Most of the fishways are located inland and they are meant not only for salmonids but also for various freshwater species. The number of fish entering fishways is relatively small in Finland, and thus space is not a limiting factor in designing them.
In Finland, studies on fishways have increased with the increase of fishway construction. Fishways, fish habitats and combined structures for fish and human needs are the objects of increasing interest. For an optimal result, the function of fish migration facilities should be studied considering the biological, hydraulic and structural viewpoints simultaneously. Such studies have been carried out mainly at the University of Oulu and at the Helsinki University of Technology.
Studies on fish passage at the Helsinki University of Technology began in the beginning of the 1980’s. They have been bound to the studies on environmental river engineering. The concept of environmentally acceptable river engineering and restoration aims at conservation and restoration of structural and functional diversity in running waters. One fishway project of the Technical University of Helsinki worth mentioning is the rehabilitation of the Vanhankaupunginkoski Rapids in the River Vantaanjoki. The project included both physical modeling of the reconstruction of the previously built fishway and numerical modeling of flows below the fishway (e.g. Laasonen & Rytkönen 1999). Other recent case studies have been, for example, the restoration of Myllypuro Brook in Nuuksio National Park, the improvement of the River Tuusulanjoki, and the flood control project of the River Päntäneenjoki (Helmiö & Järvelä 1998, Järvelä & Jormola 1998, Järvelä & Helmiö 1999). Studies on fishway hydraulics have covered, among other things, numerical and physical modeling of flow patterns inside a vertical slot fishway with alternating slots (e.g. Laasonen 1995).
Fishways have been studied at the University of Oulu, Finland, since the early 1980’s, with an interdisciplinary basis. The main goal of the fishway research was initially to determine the conditions in fishways based on fish behavior and physiology, and then develop guidelines for construction. The swimming behavior of fish has been studied in small experimental fishways, at migratory obstacles, and in a natural swimming route of migratory fish (Hooli 1988, Heikkilä & Hooli 1989, Laine 1990, Laine et al. 1998). Fishway hydraulics has been studied in existing fishways and in laboratory scale models. Laboratory scale model studies on fishway hydraulics have been carried out on a larger scale since 1991 (App. 1). Most of the hydraulic studies at the Hydraulic and Water Resources Engineering Laboratory during 1991-95 were conducted for practical purposes. In 1996, the new experimental hall was adopted for use, and since then, more theoretical studies have been conducted. The results of the fishway studies have been used in improving the conditions for fish migration in several existing fishways and in designing new fishways. In evaluating the applicability of hydraulic operation and the optimal structure of fishways, fish biologists and civil engineers have worked together in close co-operation.