DISTRIBUTION AND MIGRATORY BEHAVIOR OF ADULT WILD AND FARMED ATLANTICSALMON (SALMO-SALAR) DURING RETURN MIGRATION

Migratory behaviour of adult wild and fanned Atlantic salmon during th e last phase of the marine migration was analysed by radiotelemetry ou tside a large North Norwegian river. By tagging 39 wild and 40 recentl y liberated farmed adult salmon in the fjord, distribution to rivers a nd migratory speed of salmon was estimated. The wild salmon studied ha d most probably originated from the River Alta, whereas the farmed fis h had no earlier freshwater experience from the area of release. A hig her proportion of the tagged wild fish (87%) than farmed (50%) was rec orded in the River Alta. Farmed sermon spent a mean of 106 h in the se a from release to entering the River Alta, while the corresponding fig ure for wild salmon was only 41 h. The results suggest precise homing to the River Alta in wild salmon, while released farmed salmon showed a more random distribution to neighbouring streams. The present result s further suggest that large :rivers attract higher numbers of escaped farmed salmon than small rivers.