A unique research experiment in Finland: Testing release of captive bred pearl mussel juveniles
In 2016, researchers of the Ģֱ found that the freshwater pearl mussels (Margaritifera margaritifera) of River Mustionjoki and River Ähtävänjoki had stopped reproducing. Mussels from these rivers were transported to Konnevesi research station at the Ģֱ in autumn 2016. Intensive care and feeding in tanks of the research station improved condition of the mussels, leading to recovery, successful reproduction and production of glochidium larvae in 2018.
Glochidia were attached to gills of salmon and trout, obligatory hosts, where developed until detaching in 2019 as small juvenile mussels. Those juveniles were grown for a year in plastic boxes, until they reached the length of 2-3 millimeters—big enough to test their survival in natural conditions.
Now the tiny pearl mussel juveniles are returned to their rivers of origin in mesh-covered hole plates. Each juvenile has an own, numbered compartment in the hole plate, so that their growth and survival can be monitored individually.
“This 4-month test will give us important information for the future and yield valuable research material”, says Professor Jouni Taskinen from the Ģֱ. He is leading the captive breeding research.
The main release of the juveniles will take place in 2021, after reaching the age of 2 years and length of 4-5 millimeters.
“It is good to know that these mussels reach maturity not until they are 20 years old, and their life span can exceed 200 years”, reminds Jouni Taskinen.
Captive breeding is needed to save pearl mussel populations
Freshwater pearl mussels live in pristine rivers. Fine sediments fill the interstitial spaces in bottom gravel, suffocating the juvenile mussels who live their first years burrowed in the gravel. Migration obstacles and overfishing have wiped out salmon and trout populations leaving mussels without obligatory host fish.
“When old pearl mussels stop producing larvae, a slow dying-out of the population starts. Our results show that it is possible to rehabilitate the poor condition, old mussels in captivity, and eventually restore their reproductive functions. Now it is the last possibility to give a helping hand to River Mustionjoki and River Ähtävänjoki (in the picture) pearl mussels, because their numbers are sinking at an alarming rate”, notes Jouni Taskinen.
Link to Freshabit LIFE IP –project:
More information:
Konnevesi Research station, Ģֱ: Prof. Jouni Taskinen, jouni.k.taskinen@juy.fi, tel. +358 40 355 8094 and mussel-keeper Hanna Suonia, hanna.m.suonia@student.jyu.fi, tel. +358 40 7777 566
Freshabit LIFE IP –project, Metsähallitus: Jari Ilmonen, jari.ilmonen@metsa.fi, tel. +358 40 831 8307
Communications Specialist Tanja Heikkinen, tanja.s.heikkinen@jyu.fi, tel. 358 50 581 8351
The Faculty of Mathematics and Science:
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