High incidence of hatchery origin Atlantic salmon in the smolt output of a Canadian River

• Published in: ICES Journal of Marine Science
• Main Authors: Stokesbury, M. J., Lacroix, G. L.
• Format: Text
• Language: English
• Published: Oxford University Press 1997
• Subjects: Articles; Atlantic salmon; Salmo salar
• Online Access: http://icesjms.oxfordjournals.org/cgi/content/short/54/6/1074; https://doi.org/10.1016/S1054-3139(97)80011-2

The origin of Atlantic salmon ( Salmo salar ) in the smolt migration from the Magaguadavic River, New Brunswick, was examined to assess the importance of losses of juveniles from hatcheries and the potentialimpact on the wild stock. Three hatcheries that produce over two million smolts annually for the aquaculture industry are located along the river. Smolts were sampled at the mouth of the river over a 1-month period. Two methods were used to determine their origin: (1) external appearance of fins and size at a given age, and (2) a discriminant function analysis comparing number of circuli in the first year on scales and back-calculated length at age 1 to those of fish of known wild and hatchery origins. The two methods indicated that 23.4–39.6% of smolts were of wild origin, 9.4% were hatchery releases, and 51.0–67.2% were juvenile escapees. The fin and size method predicted that more smolts in the run were of escaped hatchery origin than classified by the discriminant function analysis. Many of these were large 1-year-old smolts. Smolts of hatchery origin were significantly larger than wild smolts and could benefit from increased early marine survival. This study indicates that the potential impact of juvenile salmon that escape or are accidentally released in rivers has probably been underestimated.