Limited spawning grounds threaten salmon population in Kokemäenjoki River, Finland

The Kokemäenjoki River has a limited area suitable for the spawning of salmon. Current estimates indicate that there are only about 15 hectares of adequately productive spawning grounds in the main river and another 13 hectares in its tributaries. Recent studies suggest that even the construction of fish passages at dams would not significantly improve this situation, according to a statement from the Varsinais-Suomi Centre for Economic Development, Transport, and the Environment.

Restorative efforts in the riverbanks could potentially increase the area of suitable spawning grounds to a maximum of 59 hectares. In contrast, the Iijoki River in northern Finland boasts an estimated spawning area of over 800 hectares. The lack of spawning sites for salmon can be attributed to the nearly complete damming of the Kokemäenjoki, where almost all of the river’s elevation drop is harnessed for hydropower, leaving no natural rapids or suitable habitats for salmon.

According to fisheries biologist Leena Rannikko, realistic prospects for broader restoration efforts for the salmon population remain slim unless there is a significant change in the river’s damming and regulation practices. Additionally, analyses of echo sounder data reveal that last year, approximately 105 to 288 larger salmon and 21 to 93 smaller salmon ascended the Kokemäenjoki.