Large-Scale Escapes of Farmed Atlantic Salmon ( Salmo salar ) into Norwegian Rivers Threaten Natural Populations

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Gausen, D., Moen, V.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1991
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1139/f91-055; http://www.nrcresearchpress.com/doi/pdf/10.1139/f91-055

We present data on Atlantic salmon (Salmo salar) which show that escaped farmed salmon enter Norwegian rivers in great numbers. Escaped farmed salmon comprised a substantial proportion of the mature salmon present on the spawning grounds in autumn. A potential for large-scale genetic introgression thus exists. The sex ratios, length distributions, and times of ascent of wild and farmed salmon differed significantly, reflecting major variations in biology and behavior. High proportions of farmed salmon (> 20%) were found only in rivers having fish farms situated closer than 20 km from the outlet.