Homing experiments with parr, smolt and residents of anadromous Arctic char Salvelinus alpinus and brown trout Salmo trutta : transplantation between neighbouring river systems

• Published in: Ecology of Freshwater Fish
• Main Authors: Nordeng, H., Bratland, P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2006
• Subjects: Ecology; Aquatic Science; Ecology, Evolution, Behavior and Systematics; Arctic; Salangen; Salvelinus alpinus
• Online Access: http://dx.doi.org/10.1111/j.1600-0633.2006.00188.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1600-0633.2006.00188.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1600-0633.2006.00188.x

Abstract – Olfaction is decisive for the homeward migration of anadromous salmonids. Two different olfactory hypotheses for explaining how this mechanism works have been proposed (the imprinting and the pheromone hypothesis), and they differ with regard to the origin of the odours that define home. The pheromone hypothesis assumes that fish respond to strain‐specific pheromones and that no imprinting is necessary. The imprinting hypothesis assumes that juvenile fish become imprinted to odours of abiotic or biotic origin in natural rivers; the imprinting may be a single event or may occur sequentially during downstream migration as smolts. The two hypotheses were challenged by reciprocal transplantation of parr, residents and smolt of Arctic char ( Salvelinus alpinus ) and brown trout ( Salmo trutta ) between the Salangen and the Løksebotten rivers. Both rivers empty into the Salangen Fjord, Norway, about 10 km apart. Salangen Arctic char released in the Løksebotten River, and Løksebotten brown trout released in the Salangen River (parr, resident and smolt) initiated spontaneous homeward migration without preceding contact with home stream water. This indicates that site imprinting (single or sequential) could not have been involved. In the sea, the released fish apparently integrated into the migratory system of relatives from their river of origin. Recapture rates did not differ for fish allowed to receive single or sequential imprinting.