The Purtse River is among the rivers with the most rapids, and historically has been one of the best salmon rivers in Estonia. The biota of the river, in the meantime, had unfortunately essentially died out, as a consequence of human activity, but since the end of the last millennium, it had started to recover gradually. This has been aided among others, through the restriction of pollution, removal of migratory barriers, as well as the systematic restocking of salmon. The removal of residual pollution has also been started, from the river and its tributaries, with the support of the Cohesion Fund. The Erra River will be cleaned of re4sidual pollution, to the extent of 1.5 km, in the framework of the LIFE IP CleanEST project, while the rest of the river will be cleaned, with the support of the Cohesion Fund.
Dams have been torn down and fish ladders established, in order that highly migratory species reach the spawning grounds, as well as to ensure the free movement of fish both upstream and downstream. There is one migration obstacle left on the Purtse River, which is impassable for fish - the Püssi dam. This is a site amongst the highest of priority, within the LIFE IP CleanEST project. The ongoing monitoring has shown that the Sillaoru fish ladder, established downstream from the Püssi dam, functions and that the old dam ruins do not hinder the movement of fish. Both salmon, sea trout, as well as the European river lamprey that has poorer swimming capability, reach up to the Püssi dam.
The Purtse River has been since 2005 been populated with over 800 000 juvenile salmon, in order to accelerate the restoration of the Purtse River salmon stock. Fry as well as, one summer, one year, two summer and two year juveniles have been released. It is necessary, within the next 5 years, within the framework of the LIFE IP CleanEST project, to populate at least an additional 100 000 juveniles that are required to create a self restoring salmon stock.
The Purtse River, in 2020, with the support of the project, was populated with 12 100 one year and 3 200 two year salmon juveniles.