Farmed Atlantic salmon (Salmo salar) in fisheries and rivers in Norway

Abstract

The proportion of reared Atlantic salmon in Norwegian marine and freshwater fisheries was estimated using a combined method of examining external body morphology and scale patterns of the salmon. The point estimates suggested a high proportion of reared salmon both in the fisheries and in salmon spawning populations. During the fishing season in summer, the proportion of reared salmon was higher in the outer coastal areas than in fjords and rivers. Near spawning, the proportion of reared salmon in many rivers increased considerably, indicating that these fish ascend the rivers late in the season. Several sources of error affect the estimates, but there are strong indications that the proportion of reared salmon in nature has increased considerably in recent years. This is probably a result of the increased salmon farming activity in Norway, and the subsequent increase in number of salmon escaping from fish farms.