Case study:Restoration of spawning grounds for trout in Bjornesfjorden (Hardangervidda)
Project overview
| Status | Complete |
|---|---|
| Project web site | |
| Themes | Environmental flows and water resources, Habitat and biodiversity, Hydropower, Hydromorphology |
| Country | Norway |
| Main contact forename | Nils Runar |
| Main contact surname | Sporan |
| Main contact user ID | |
| Contact organisation | Statkraft AS |
| Contact organisation web site | http://www.statkraft.no |
| Partner organisations | Uni Reserch Miljø LFI, Numedals-Laugens Brugseierforening (NLB), The Norwegian Water Resources and Energy Directorate (NVE) |
| Parent multi-site project | |
| This is a parent project encompassing the following projects |
No |
Project summary
The Bjornesfjord was temporarily lowered in 1959 to provide water for hydroelectric powerplants (Noreverkene) in Norway. This resulted in permanent damage to several spawning grounds for trout, as the original spawning-substrates were removed. This meant that the substrate of the affected spawning areas became dominated by sand and that the areas were no longer suitable for spawning. To compensate for the damage caused to the fish stock in connection with the lowering of water in the fjord, an order was issued for the release of trout. In the period between 2002-2006, LFI Uni Miljø, in collaboration with NLB, Statkraft and NVE, restored spawning areas in the Bjornesfjord. The restoration was carried out by laying gravel in the outlet of Lågaros, in the Nøresundet and Meinsbusundet. These areas had been adversely affected by the lowering of the fjord in 1959.
Subsequent surveys in 2007 and 2013 show that the restoration worked as intended, with spawning occurring each year on the newly established spawning grounds. The measures, therefore, helped to bring spawning conditions towards the natural state that existed before the lowering.
Monitoring surveys and results
Lessons learnt
The establishment of flow deflectors and the laying of rocks, blocks and uprooted trees in areas with previously low hydromorphological variation, have great potential for the improvement of the aquatic environment and habitats - in this example, fish production increased in the rehabilitated areas.
Higher densities of both “yearlings” and older juvenile fish were found in the habitat-improved areas than were found in the control sites.
The flow deflectors led to a better spatial distribution of spawning opportunities for lake trout in the upper part of the Teigdal river.
It could have been advantageous to place more blocks and stones in the riverbed to increase the extent of the measures and thus the quality of the habitat in the habitat-poor areas. An analysis of the total available area in the three habitat-improved areas shows that only 2% of this area had been improved. An increase would further enhance the habitat and lead to a higher fish production.
Image gallery
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Catchment and subcatchment
Site
Project background
Cost for project phases
Reasons for river restoration
Measures
MonitoringHydromorphological quality elements
Biological quality elements
Physico-chemical quality elements
Any other monitoring, e.g. social, economic
Monitoring documents
Additional documents and videos
Additional links and references
Supplementary InformationEdit Supplementary Information
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