Frilund GE, Koksvik J, Rikstad A and Berger HM. 20092009. Cottus gobio (Linnaeus, 1758), a new fish-species in Nord-Tr ndelag County, Norway. Fauna Norvegica 29: 55-60. Cottus gobio, a freshwater sculpin, was discovered by electrical fishing in rivers draining to Murusj en in Lierne, Nord-Tr ndelag County in the middle of Norway. Until now, this sculpin has only been found in a few river systems in the south-eastern and north-eastern parts of Norway. Species specific characters (glands and fins) were used to distinguish C. gobio from the close relative C. poecilopus. The sculpin dominated the catches in all the investigated rivers. In August 2008 in the River Fiskl ysa, a total of 194 specimens were collected. Their length varied from 37 mm to 105 mm, indicating the presence of both juvenile (age 0) and adult individuals. In September 2008, qualitative sampling was conducted in another part of Fiskl ysa and in the rivers Kveelva and Murubekken. In River Fiskl ysa, the species was not registered above a presumably impassable waterfall about 1.6 km from Lake Murusj en. In River Kveelva sculpins were caught below a nine meters moderate waterfall, close to the outlet of Lake Kvesj en, but no sculpins were registered above the waterfall. This indicates that the waterfall is a possible barrier for further upstream dispersal into Lake Kvesj en. Sculpins were also registered in River Murubekken.The paper discusses possibilities for C. gobio being spread naturally or artificially into the river systems in Lierne. It is predicted that the dispersal most likely has been natural from populations in Sweden, as there are no distinct barriers preventing the sculpin from spreading westwards. The time-period of the dispersal, however, is still unknown, and the sculpin may still be expanding its home range in these water systems.