In early May some 30,000 fish are released into the straight next to the Royal Opera House in Stockholm, known locally as "Strömmen" (the stream). As part of a conservation effort that began in 1973, the city of Stockholm celebrates this event every year. Strömmen offers exciting fishing in an unusual fishing environment with more than 30 different species contributing to the fishing industry. Every year, large amounts of sea trout and a small number of salmon are caught. The fishing area extends from Riddarfjärden all the way to Djurgården.