Konnevesi brings new hope for the freshwater pearl mussel
River and creek waters suitable to thefreshwater pearl mussel are nowadays scarce in Finland.
The species has suffered for various reasons. Many traditional mussel rivers have been blocked with dams, and it has prevented the migration of salmon-type fish up the river, which would be crucial for the mussel’s reproduction. Moreover, as streams or riverbed have become clogged with silt, it has been bad for the mussels: The freshwater pearl mussel needs streams with a gravel bed, where clear water, rich in oxygen, is flowing.
If the riverbed is clogged, water does not flow properly, and the fine-grained silt blocks the gills of the juvenile mussels.
Researchers at the Konnevesi Research Station, Ģֱ, began to take measures in 2016 to save freshwater pearl mussels.
The first batch of 100-year-old mussel individuals in bad condition were brought to recover in the research station’s nursery pools from the Mustionjoki and Ähtävänjoki rivers.
After that, there have been plenty of new arrivals. The pools are full, new juveniles are produced all the time, and there is currently no room for new mussel populations. This work is unique, as the research station’s institutional nursery is the only one in Finland.
Freshwater pearl mussels have already been transferred to Konnevesi from altogether 12 rivers or streams from different parts of Finland.
The research station staff felt the joy of success when the first juvenile mussels produced in Konnevesi were returned to their home river in summer 2021.
“When the juveniles are taken to the river habitat, they are already energetic and ready to filter in nutrition,” says Research Coordinator Heidi Kunttu from the Ģֱ.
“Returning takes place by means of gravel boxes. The juveniles live first in the safety of the boxes.”
Kunttu is specialised in molecular biology and works as part of Professor Jouni Taskinen’s research team. She has monitored the life of freshwater pearl mussels in Konnevesi for three years now. Most of the mussel rehabilitation and research work in Konnevesi is currently funded by the LIFE Revives project.
Hard work at the research station – and busy reproduction
It is estimated that there are only about 150 freshwater pearl mussel rivers remaining in Finland.
As a researcher, Heidi Kunttu has developed an affective bond to this endangered mussel species of our rivers. It began in summer 2021 when she was taking care of small mussel juveniles in Konnevesi.
“For me, the mussels are personas hanging around there in the pool,” Kunttu describes.
At the station, the care of mussels is arduous, round-the-clock work.
“We must keep the conditions in the pools constantly suitable to the species,” Kunttu explains. “The water must be rich with oxygen, algae nutrition must be evenly available, and the streaming conditions should be optimal.”
The conditions in Konnevesi have been favourable enough to revive old mussels to a successful reproductive condition again, so that the research station produces now tens of thousands of juveniles per year.
After a good reproductive year, a mussel may spend a couple of years in recovery, Kunttu says.
The freshwater pearl mussel begins life as a tiny larva, known as glochidia, which attaches itself to the gills of salmon or trout to develop there for a year.
“And when the larvae then drop out from there, they are still tiny, less than a millimetre long,” says Heidi Kunttu. “To the naked eye, the larvae look like grains of sand, but viewed through a microscope lens they already appear as tiny mussels. When the juveniles are returned to river water, they are slightly under three millimetres in size.”
Freshwater pearl mussels live a slow-paced life, but they clean water at a great speed
At the Researchers’ Night at the Ģֱ, the audience can view tiny freshwater pearl mussel juveniles through a microscope. There are also duck mussels on display to demonstrate how water is cleaned in their filtering process.
The old and dignified living freshwater pearl mussels, however, will remain peacefully in their nursery tanks at the Konnevesi Research Station. They will not be transported to Jyväskylä.
Heidi Kunttu thinks that, despite the attention the mussels have received in the media, this ancient inhabitant of streams is not a familiar animal to many. In her opinion, everybody should know at least these five points:
Freshwater pearl mussels live a slow-paced life, but they clean water at a great speed. |
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| 1 | In Finland, the freshwater pearl mussel became protected in 1955. The species is extremely endangered. It is estimated that Finland has about 150 rivers where the freshwater pearl mussel is still living. However, only in about ten of these do the younger generations can survive. |
| 2 | The freshwater pearl mussel is an important umbrella species. One single mussel and its gills can clean up to 50 litres of water a day. In this way, the species creates a favourable habitat for many other organisms. The mussel is useful for fish, for example: When it is feeding, it spits extra material to the riverbed for various insect larvae and fish to feed on. |
| 3 | The freshwater pearl mussel is a good indicator species. If there are these mussels in a river, other species also have good conditions. |
| 4 | The freshwater pearl mussel is a long-living species. The oldest discovered individuals have been as old as 280 years. Its different life stages are also slow: It takes from five to six years before a young mussel even peeks out from its shell when lying in the gravel on the riverbed. |
| 5 | If you find a freshwater pearl mussel, leave it alone! The mussel’s remains, meaning the shells or shell pieces found in a river, must also be left intact. |
