Professor, cand. real. Hans Nordeng died in Baerum, Norway in May 2010, at the age of 91 years. He was an extraordinary man; an unconventional, creative and hard-working scientist, and a very gifted teacher and tutor. Most of his publications were based on many years of research, often combining extensive field work and carefully planned experiments and transplantations (Vollestad and Skurdal 1994). Several of them contributed significantly to the fields of fish ecology and evolution. He kept a glowing enthusiasm for fish biology until a great age, publishing his last paper when he was 91 (Nordeng 2009). He grew up in Salangen, Northern Norway, close to the river that was to become the primary research system of his career. As a young recruit at an under-officer school, he fought in the battle at the Narvik-Gratangen front of World War II in the spring of 1940. He started a military career after the war but later went to university as a grown-up man. After graduation, he held an assignment with the Institute of Marine Research in Bergen before taking up a lectureship at the University of Oslo, a position he kept for most of his active life. Then, after retiring fromOslo, he was appointed as a full professor at the University of Tromso, finally achieving the personal chair he so much deserved. He served in this position for 2 years. Hans Nordeng published several innovative and influential papers. Two of them will always be tied to his name. The first, published in Nature (Nordeng 1971), proposed a pheromone hypothesis to explain the population specific homing of anadromous fishes to their native river. It was based on transferring fertilized eggs of anadromous arctic charr (Salvelinus alpinus) from the Salangen River system to a hatchery at Voss, south-west Norway (south of the range of anadromous charr), rearing the fish to the smolt stage (4 years), flying them back to northern Norway and releasing them in the estuaries of the Salangen River and a neighbouring river. These fish had experienced no olfactory cues from their home river water during rearing. Yet almost all the fish that were released in Salangen and the majority of the fish released in the other river, returned to the Salangen River. This strongly suggested that population specific pheromones, possibly bound to the skin mucus, provided the olfactory cues for homing; not the river water itself. He established important co-operation with physiologists to test the hypothesis (Doving et al. 1974), and successive pheromone research included several other migratory fish species. The second paper (Nordeng 1983) was based on his long-term studies of three sympatric Environ Biol Fish (2011) 91:367–368 DOI 10.1007/s10641-011-9793-3