In 1924, Vattendomstolen (the Water Court) gave Dalälvens Vattenregleringsföretag ("Dalälven Water Regulation Company") permission to regulate the water level of Siljan with a variation of 1.88 m. The biological consequences of such an intervention in nature were acknowledged. The decision therefore required the power station builders and the regulation companies to safeguard the fish population by establishing a fish farm in Sollerö Parish. The fish farm was established on the north point of Sollerön in 1926.
Prior to the decision, a study had been carried out on the impact of the regulation on the various fish species. It was concluded that the spring-spawning fish species such as pike and perch would benefit from the regulation, while the autumn-spawning fish, especially whitefish, would suffer. Therefore, whitefish would be the first species to be farmed. Roe was collected mainly in Ryssa and Limån, and by net fishermen further out on Siljan.
Soon, pike farming also began. The fish farm's large motorboat shuttled to release fry or collect roe. Bicycles and cars were also used.
In the 1940s, there was an increased demand for larger fish for releasing where regulatory damage had occurred to the fish stock. This was particularly true for salmon trout, char and brook trout. At that time, fish farming was expanded with a farming pond in Ryssa. Eventually, 7 more ponds and about 40 wooden basins were built as the demand for larger fish increased further. Rainbow trout became very popular.
Truckloads of fish went to northern Dalarna, Härjedalen, Värmland, Hälsingland, Västmanland and southern Dalarna. Hatches of whitefish and pike fry reached huge numbers. Some 7-8 million pike and 6 million Lavarets (European Whitefish) were produced per year and in the late 1950s, grayling farming began.
From 1960 to 1969, five new power stations were built in Österdalälven, disrupting the herring spawning grounds. Roe was collected downstream of Spjutmo for hatching and rearing into 2-year-old and 3-year-old fish. Between 1972 and 1975, the fish farm managed to deliver more than 258,000 herring trout. Half were released in Österdalälven and half in Siljan. The Siljan trout, or Siljan salmon as it is also known, is a big game fish from ancient times when Siljan was a bay of the Baltic Sea. Human exploitation led to the decline of the viable population. One of the tasks of the fish farm was to restore the hard-hit stock of the Siljan salmon
Fish farming ceased in the early 1980s.
Work continues strengthening the Siljan salmon (Siljan trout) stock. Salmon ladders past power stations and dams are planned and built along Österdalälven. Diversions are also planned in the smaller rivers along Siljan (e.g., Mångån) so that the fish can migrate and spawn in forest lakes.