Rescue efforts for critically endangered freshwater pearl mussels begin in Hukkajoki, Suomussalmi

The second week of work to rescue the critically endangered freshwater pearl mussels began on Monday in Hukkajoki, Suomussalmi. Eero Moilanen, a nature expert from Metsähallitus, stated that the restoration efforts are primarily conducted using shovels and by hand. “I estimate it will take a couple of weeks just to clean the most affected areas. We won’t be able to restore everything completely,” he added.

Currently, the focus is on repairing the ruts caused by heavy machinery. “First, we will dismantle the ruts where fine sediments have compacted under the weight of the machines. We are aiming to match the depth to that of the untouched river above,” Moilanen explained. Once sufficient sediment is removed, the ruts will be covered with rocks and landscaped to resemble a natural environment, potentially using moss stones from undisturbed sections.

After fixing the ruts, Metsähallitus will clean the downstream areas heavily impacted by sediment from the machinery, with mud extending up to a kilometer from where the machines crossed the river—most severely over a span of about 100 meters. The sediment will be deposited far enough from the river to prevent floods from returning it to the waterway.

Assistance has been promised by Stora Enso, with around 30 workers joining the restoration efforts this week, significantly enhancing the speed of the operation. Moilanen expressed optimism about this collaboration, noting that the work would progress much faster than it would with their 12-person team.

Professor Jouni Taskinen from the University of Jyväskylä believes it is unlikely that Hukkajoki will fully return to its original state. He mentioned that for the reintroduction of mussels, a suitable environment and juvenile production must be ensured. Furthermore, he noted the challenges created by insufficient buffer zones around clear-cut areas. It is estimated that over 120,000 critically endangered mussels inhabit Hukkajoki, accounting for about five percent of the species’ population in Finland.