The most significant fishing grounds in Kajaani are at Linnanvirta, the Ämmäkoski-Tullikallio area, Lake Iso-Ruuhijärvi and Lake Oulujärvi.
Although Kajaani’s rapids have been harnessed to produce power, River Kajaaninjoki has remained a popular fishing destination. Right in the heart of the city, there are anglers almost year-round fishing in the Linnanvirta section of the river, which surrounds the castle ruins. Linnasaari Island, the site of these ruins, as well as the riverside parks and the old tar pier Tervalaituri provide ease of movement and guarantee the availability of good-sized trout, grayling and whitefish within casting range. The lower part of the Ämmäkoski Rapids also belongs to this fishing area. Although there is a no-fishing zone right below the dam, fishing is permitted along several hundred metres of the northern bank. Trout, whitefish and, in recent years, pike-perch enter the river from Lake Oulujärvi.
Below the hydro-electric plants is the Renfors building. In the area in front of it, dozens of large trout have been caught, with the record-breaking ones weighing almost ten kilograms. From the Kalkkisilta quay by the Renfors building, you can access the fishing waters of Lake Oulujärvi by boat. The Renfors family manufactured fishing equipment in the late 19th century, and their traditions are celebrated at the Finnish Fly-tying Championships in Kajaani.