How have hydroelectric dams affected salmon and sea trout in Finland?

In Finland, the construction of dams for hydroelectric power has adversely affected the natural spawning habits of salmon and sea trout. These structures, along with river pollution, have disrupted the migratory paths necessary for these fish to reach their traditional spawning grounds.1

To mitigate these impacts, Finland has established a large number of fish-breeding stations where artificial spawning is induced to help maintain fish populations. While technologies such as fish ladders and fish locks are used globally to help fish bypass dams, the success of such measures can be difficult to sustain as the number of dams on a river increases.12