The Merikarvia River begins from a dam at north end of Isojärvi, and flows into the Bothnian Sea from Merikarvia. The river is 27 kilometers long, 35 meters above sea level, and has an average flow of approximately 15 m3/s. Migrating fish have a clear route upstream for the entire length of the river. The river’s only fish ladder is in Lankoski, 22km from the river’s mouth. The fish ladder was part of the river’s stream restoration project in 1996.

In 1990’s the three municipalities with ownership to the Merikarvia River formed a nonprofit group called The Merikarvia River’s Kalakierros. The group is responsible for managing the Merikarvia River’s fisheries, fish stock care, waste management, and maintaining resting places, trees, etc. The collective fishing permit area formed by the municipalities is 24 kilometers long. The area has approximately six kilometers of rapids, the largest of which are Lankoski, Puukoski, Stäävitkoski, Vaadinkoski and Holmankoski.

The river’s abundant fish stock is maintained by fish stocking, which has been made possible by the increase in fish permit income. The river is frequented by thousands of pole fishers each year, accumulating approximately 10,000 days of fishing yearly.

While trout stocking has been done with trout of varying ages, most of it has been with two year old migrating trout. In 2011 Kalakierros stocked approximately 20,000 two-year-old migrating trout and 14,000 fry. Rapids are stocked with 6,000 to 7,000 kilograms of catchable size rainbow trout each year, which on average weigh 1-3kg, but the largest can get up to 4-8kg. Kalakierros also stocks some migrating European whitefish and grayling. Salmon stocking is done mostly by the government.

The Merikarvia River is Finland’s first river with migrating fish that has a voluntary net fishing ban. This ban reaches up to 5 kilometers to the sea from the mouth of the river. This guarantees fish an unobstructed ascent up the Merikarvia River.