Background
The houting (Coregonus oxyrhynchus), a fish species from the white fish family, has a complex ecology making it vulnerable to relatively small disturbances in its range.
It was previously distributed throughout the Wadden Sea (the Netherlands, Germany and Denmark) but it has declined severely and its occurrence is now restricted to Denmark, where it reproduces in six river systems.
The presence of even small obstacles in rivers is one of the main impediments to successful reproduction, as the houting is unable to pass weirs and fish ladders. Silting of spawning grounds is also a severe problem. Furthermore, juvenile houting require large areas of reed beds or flooded meadows, where they forage for several months prior to migration to the sea.
Previous restocking attempts in Denmark have not been successful because they were not followed up by habitat restoration.
Objectives
The overall project objective is to restore and maintain a favourable conservation status for the houting in four Danish river systems. The project is in accordance with national recommendations. It will explore possibilities and develop recommendations for reintroduction into other parts of the houting’s previous distribution range within the EU.
The project will have a profound positive effect on all other components of the river ecosystems including the conservation status of the habitat type ‘Water courses characterised by Ranunculion fluitantis and Callitricho-Batrachion communities’.
It will also result in improved access to areas of spawning habitats for other anadromous fish species, such as indigenous populations of Atlantic salmon (Salmo salar), species of lamprey (Lampetra sp.) and the only population of weather fish/pond loach (Misgurnis fossilis) in Denmark, and it will improve habitat conditions for the otter (Lutra lutra).
Weirs and dams in the four river systems will be removed and riffles or meanders constructed in order to facilitate upstream migration. Two hydroelectric power plants and three fish farms will be decommissioned. River sections will be restored with gravel and stone, creating new spawning grounds, and a combination of changes to hydrology and construction works will create new flooded areas adjacent to the river.
The project will be implemented in broad cooperation between a number of stakeholders including local and regional authorities, land and fish farm owners, a regional angling society, and owners of hydrological installations.