It all starts from headwaters
The streams of the headwaters are in good condition if they look wild and untouched – a fallen tree here and there, water moss, a winding course, big rocks, and plenty of spawning gravel where the fish can reproduce. A straight and deep stream is rarely in its natural state: often this indicates that land drainage for forestry, clearing and channelising for timber floating or hydropower have molded the streams away from their natural state.
We have restored streams at the project locations, in order for them to provide more vital habitats for fish as well as other species. Streams are also beautiful to look at, and the restoration work also increases the pleasantness of the areas and promotes their recreational use.
The fish can pass – finally
Few animals have such love for the place of their birth as salmon do. After reaching maturity, the fish return to breed in the same waters in which their life began. Although this instinct is powerful, even the strongest of salmon cannot break through a concrete wall. In Finland, many migratory routes have been blocked by dams.
We have fixed these blocked migratory routes in seven of the project locations by building fish passes and restoring the fishes’ living environments. These measures are a good beginning, but long-term additional work is needed, including waterway restoration work and monitoring of the outcomes of this. Where migratory routes have been blocked for decades, restoring them also takes a long time.
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1
Hietama
The Central Finland brown trout has new hope. The Saarijärvi route is one of the most important lake trout passages in the region. Two fish passes were built on the route, the first of which, the Hietamankoski fish pass, was opened in May 2020.
2
Leuhu
The upper Leuhunkoski fish pass was opened in May 2021. Once opened, the fish passes opened the entire Saarijärvi route for fish, more than 500 km of stream length. The movements of the fish are monitored by camera.
3
Villamo
For 100 years, the Villamo area was one of the major migratory blocks for the sea trout in Lapväärtin-Isojoki river area. But not anymore. Thanks to cooperation between the Centres for Economic Development, Transport and the Environment (ELY) and the operator, the fish farm and waterpower plant in Villamo ceased to operate and the dam was dismantled, which opened the river channel for more than 70 km for the trout. Finally, the whole water course is open for trout migration! At the same time, approximately 700 metres of the lower riverbed was restored. Now, the fish can find shelters and possible spawning areas under the dam. Since the completion of the work in early autumn 2019, the Natural Resources Institute Finland and the Southern Ostrobothnia ELY Centre have monitored the movements of trout constantly. The four bravest trout marked with radio transmitters immediately rose to examine the sections above Villamo, and they were followed by more than 70 unmarked trout, according to the VAKI fish counter. The traffic seems to continue to be busy.
4
Hålldam
Concrete is not the only option. Two nature-like bypasses were built in the river Kiskonjoki, in the rapid of Koskenkartano, and in the dam area of Hålldam. Once they were completed, the fish will be able to migrate from the sea to lake Kirkkojärvi and tributaries by a length of approximately 45 km.
5
Koski
The rapid’s nature-like bypass is about 100 metres long, and it was connected to the old restored natural riverbed.
6
Åminnefors
A pleasant surprise was experienced on the river Karjaanjoki fish passes, although it was anticipated: The new fish pass proved to be a busy route! The fish passes of the two lowest waterpower plants of the river Karjaanjoki, Billnäs and Åminnefors, were opened in early May 2020. A fish counter and a video camera were installed on the Åminnefors fish pass to provide usable monitoring data on migratory fish. Shortly after the opening, the data showed that over 800 fish were moving up and down the fish pass during the first week. Most of them were likely to be vimbas, but also salmon and trouts have been observed. The result can be considered excellent because the migratory route was cut for nearly 70 years.
7
Billnäs
The Billnäs fish pass is a so-called vertical slot fish pass, where the fish swim from one step to another and can rest in the basins between the steps. On the bottom of the fish pass, there is a layer of natural stones of different sizes, which make the fish pass convenient also for more poorly swimming fish species and, for example, crustaceans.
The Karjaanjoki story map (in Finnish) tells the story of the freshwater pearl mussel and the salmon.
Water protection begins on the way to the rivers and lakes
Just like people, water also gets mucky as it travels its long journey. Along the way, the flowing water picks up solids and nutrients that decrease the water quality. This environmental load on the water bodies comes from the entire drainage area and is in part a natural process, but the loading caused by agricultural and forestry activities must be reduced, in order to improve the condition of the water bodies.
We have reduced the environmental load on the waterways in the project areas by using constructed wetlands and other structures that absorb the load.
Modelling can be used to forecast the amount and source of the environmental load in order to help reduce the load and strengthen water protection measures. For the first time, we have combined several loading models into a toolkit, which can be used to, for instance, illustrate how rain water can wash out solids and nutrients into the water bodies, from land that has been left bare by forest renewal.
You can learn more about the model family in the FRESHABIT drainage area restoration and modelling story map (in Finnish, opens in a new window) .
Freshwater pearl mussels get a romantic spa break
After the environmental load has been contained and the migratory fish have returned, the state of the freshwater pearl mussels will also start to improve. Currently, though, this species is still in an awfully bad state: In the rivers of southern Finland, there are mostly only old freshwater pearl mussels that are in a bad condition and do not have the strength to reproduce.
And even if they would have enough strength, their larvae need salmonid fish in order to grow, as they spend their first winter living on the fishes’ gills before then descending to the streambed or riverbed. Without salmon or trout, there is no future for the freshwater pearl mussel. Furthermore, the poor quality of the streambeds and riverbeds and the environmental load coming from the drainage area inhibit in many areas the growth of the small freshwater pearl mussels, even if there would be host fish for the larvae.
Freshwater pearl mussels from four target rivers have been rehabilitated at the Konnevesi Research Station, where the work has already borne fruit and the adult freshwater pearl mussels have begun once again to reproduce. A part of the larvae produced in Konnevesi were taken to a rearing establishment in Austevoll, Norway, where good results were achieved in reviving the Finnish freshwater pearl mussel population. Another part of the larvae were reared in Konnevesi, to gain experience in setting up a Finnish rearing establishment.
The small freshwater pearl mussels developed from larvae on fishes’ gills were facilitated at the research station, until they were big enough to be returned to their restored home waters.
The young mussels were first transferred back to their own waters initially in breeding boxes, where they can still be monitored for a couple of years. Results from the first rever-breeding year 2021-22 have been promising, showing good survival and growth for the small pearl mussels in both Ähtävänjoki and Mustionjoki.
There are many stages in the life of the freshwater pearl mussel, where everything has to go right. Adult mussels must live in densely populated communities, in order for the sperm released into the water by the male mussel, to fertilise the female.
Furthermore, the river must have suitable host fish, salmon or brown trout, which does not yet have immunity for the mussels glochidium. The host fish must be present at the same time the female is ready to release the matured glochidium larvae, for them to be able to attach to the host fish and live in its gills for their first winter.
The following summer, mussel younglings will leave the fish gills to live their first years of life in the river floor sediment, which must be rich in oxygen. Therefore, the quality of water and the river floor is one of the most important prerequisites for the viability of the freshwater pearl mussel populations.
The mussel’s extravagant reproduction strategy helps secure the survival of the species through several bottlenecks: One female can produce millions of glochidium larvae, but even in favourable conditions, only 1/10 000 of them ends up in the gills of a fish. Often, the quality in our loaded and altered flowing waters is not sufficient, and sadly, this problem is not solved even by the large number of offspring.
