He was scientific assistant and university lecturer at Department of Limnology, University of Oslo, from 1960 to 1966; research scientist at Freshwater Institute, Winnipeg, Manitoba, Canada from 1966-1977; and professor of systematic zoology in the Museum of Zoology at the University of Bergen from 1977 to his retirement in 2006.He specialized in aquatic Diptera, especially Chironomidae and Chaoboridae.