Coastal releases of Atlantic salmon, a new model for salmon ranching in Norway

Abstract

The present project is launched within the frame of a 7 year government funded programme to establish an additional livelihood for the coastal regions. The aim of the study is, through controlled experiments, to find ecologically and genetically sound release and recapture methods for salmon ranching. The coastal ranching model is based on releases from small coastal watercourses indepent large rivers with natural salmon stocks. The first releases were made in May- June 1991, when around 50 000 tagged smolts originating from three regional rivers were released in the Selstøvågen from the Selstø hatchery. The only fresh waters draining into the bay are the hatchery effluents amounting to about 2 m^3 min^-1. Prior to release the fish were acclimatized to sea water in net pens. During release the fish were surveyed by divers with underwater- video, a SIMRAD EK 500 split-beam echo sounder and fisheries sonar. Hydrography and meteorology was monitored, test fishing for predators and smolts were undertaken. The results indicate rapid westward migration of smolts and 0.1% loss of fish to predators, thus supporting the assumption that predation is a less important cause for postsmolt mortality in the marine environment.