River Simo is the other Finnish salmon river, alongside the Tornio, that drains into the Baltic Sea and has its own indigenous salmon stock. Increasing salmon spawning runs into the river have increased the popularity of fishing in River Simo.

The numbers of wild-born smolts born that migrate from River Simo to the sea have grown considerably since the 1980s and 1990s, but dropped somewhat since the peak in the early 2000s.  The current smolt runs vary between 20,000 and 40,000.

The regulation of fishing has been paramount in the recovery of the wild salmon stock of rivers Simo and the Tornio since the latter half of the 1990s. Other measures that have contributed include fish stocking and restoring rapids in the River Simo.

Research and monitoring

The salmon stock of River Simo has been studied since the early 1970s. LukeThe most important ways the Luke Natural Resources Institute Finland monitor the salmon stock include: compiling fishing and catch statistics, counting salmon spawners by hydroacoustics, estimating the density of salmon juveniles in the river by electrofishing surveys, and assessing the number of smolts by smolt trapping surveys.

The information is used in the salmon management in the Baltic Sea and River Simo. The information is used by, among others, the International Council for the Exploration of the Sea (ICES), the European Commission, and Finnish and Swedish fisheries authorities.