Many animals and plants that live in streams are dependent on migration during certain stages of their lives, to spread and to reproduce. For fish, migration is vital in order to move between spawning grounds, nursery grounds and feeding grounds.
The project Remibar has removed migratory barriers in five larger water systems in the northern part of Sweden.The work was conducted within the network of Natura 2000, and the goal was to improve the conditions for the target species salmon, freshwater pearl mussel, bullhead and otter, along with their habitats. The project represents one of the largest freshwater initiative in Sweden. A total of 300 migratory barriers, both culverts and dams, have been removed.
In Sweden there is a road crossing approximately every second kilometer of a stream and of these at least 30% are barriers to fish and other aquatic species. There are also dams, remaining from the log-driving period, which are no longer in use but still makes barriers. Through removing barriers we have created connectivity within the streams and thereby improved and secured the conditions for the targeted species as well as for other species that thrive in or along the streams.
What are the problems?
Culverts can cause different kinds of migration barriers. Some of the most significant are:
- Water velocity is high.
- Lack of resting sites for fish.
- Low water level within the culvert.
- Perched crossings – that is, the culverts level is above the river bed at the outlet.
- Bridges or culverts lacks natural shores, and is thereby a barrier to terrestrial animals.
There are several solutions to the problems:
- Replacing the existing culvert with a bridge or an arch so that a natural riverbed can be remediated. The water velocity will decrease and resting places for fish is created.
- Replacing the existing culvert with a larger dimension lower the water velocity.
- Lowering the existing culvert, this is only possible if the dimension of the existing culvert is correct.
- Step-pools downstream the culvert will raise the water level and lower the water velocity.
- Constructed shores, shelves or marking stones will lead small animals like otters to pass under the road.
Dissemination and information has been an important part of the project. Through information on our website, in brochures, signs etc. we increased awareness of problems and solutions to barriers in streams. We have had excursions and education to targeted groups such as entrepreneurs, consultants, authorities, foresters, land owners and children.
During the project time (2011-2016) 300 barriers has been removed in the Northern part of Sweden. The project budget is € 8 million and EU’s LIFE nature-fund contributes with half the sum.
Remibar is a cooperation project between the Swedish Transport Administration, The County Administrative Board of Norrbotten and Västerbotten, the Swedish Forestry Agency, The Swedish Agency for Marine and Water Management, the forest companies Sveaskog, Holmen and SCA.
barriers, mitigation, fish passage, stream crossings