Hope for the freshwater pearl mussels (FPM) in Karvianjoki
FPMs in Karvianjoki river are dying out
Karvianjoki river is located in Northern Satakunta and has been well-known freshwater pearl mussel river. According to the locals, the main river channel of the Karvianjoki river used to hold a lot of FPMs, but intensive soil cultivation and land use have changed the Karvianjoki catchment area considerably and the FPM stocks have reacted to it negatively. It is estimated that there are around 1500鈥�1700 individuals in the Karvianjoki river. The number may sound like a lot, but the poor habitat conditions, the high age and poor condition of the FPMs and the absence of young ones in the population means that the FPMs at Karvianjoki are dying of extinction if nothing is done. Restoring the main riverbed into an environment suitable for FPMs is very challenging and at the moment, the best chance and the fastest way to prevent the threat of extinction is to look for new habitats that are currently in better condition.
Juurakkoluoma, the pearl of streams in 碍补苍办补补苍辫盲盲
One restorable such site is Juurakkuluoma. The stream runs through a natural-like spruce forest, and there are plenty of buffer zones. According to the measurements, the water quality is also good, except for iron values, which is a problem in almost every side stream in the Nothern Satakunta region. The trouts are actively introduced in to the stream, and based on test fishing, the trout population in the stream is good. Also, according to preliminary FPM juvenile tests, Juurakoluoma could also be suitable for FPMs.
Renovations towards a better living environment
Even though Juurakkoluoma is in almost natural condition, the need for restoration was seen during the field inspection sessions. Sand was accumulated in the promising trout spawning areas, and we wanted to establish areas for the FPMs, if the juvenile or adults are brought to Juurakkoluoma in the future. Before starting the work, a restoration plan was made and permission to deviate from the protected area's conservation regulations was sought from the ELY Center. Finally, a contractor was tendered for the restoration work. It was a pleasure to notice that many experts were interested about the works at Juurakkoluoma.
The restoration work was carried out between 29.10.-1.11. and done mainly by handwork and manpower. The gravel was used to make various spawning gravel pits and places for the trout, and larger stones were placed next to them as hiding places. Larger stones also break the monotonic flow and diversify the bottom of the stream.
Juurakkoluoma meanders at the bottom of the steep stream canyon, so transporting the materials was challenging at times. With the help of the ATV and trailer, the gravel and wood material could be transported down the slope and close to the stream. During the first days, our renovators from Raktiva Oy came up with the idea of transporting stones along the the so-called rock slide, which made the work much easier.
In addition to the graveling work, wood restoration work was carried out on the stream. Juurakkoluoma originally had quite a bit of woody material, and by adding it, the stream environment was diversified. Different structures were placed in the stream to divert sand away from the gravel areas, to increase the flow or to otherwise diversify the stream bed. In total over 30 wooden structures, 5 spawning areas for trouts, 4 gravel pits for FPMs, stoning the stream bed at 4 areas and restoring river bed with Hartijoki method at 4 areas were carried out in Juurakkoluoma along 300 meters.
Students involved in renovation works
The LIFE Revives project strongly includes the spreading of FPM awareness and school student cooperation. A good opportunity for this opened up during the restoration work, when a group of 15 high school students from Honkajoki School arrived to learn about stream restoration. The school has a versatile environmental education included to their studies, allowing students to learn a variety of things about nature and the environment in a concrete way. Participating in stream restoration and hearing about the life of trout and FPM was certainly a good addition to the students' environmental awareness. Concrete promotion of biodiversity often teaches more than reading about it from the books. For many, the renovation work also seemed like fun, and the rock slide in particular was funny elements for the students.
Work for the FPM continues in Northern Satakunta
Although the restorations have been completed for the year 2024, the work must continue in order to guarantee the future of the Karvianjoki FPM. Now the restored areas will be monitored with different methods until the end of the project and the LIFE Revives project has explored the possibilities of restoring the rapids of Karvianjoki in order to provide more habitat for the FPMs living in the main stream. Land owners and water area owners will be contacted about the topic during the spring of 2025. We eagerly wait to see how Juurakkoluoma's restorations and their effects on the trout stock and possibly the FPM develop.
Author: Lotta M盲kinen, coordinator of LIFE Revives in Centre of Economic Development, Transport and the Environment of Southwest Finland