REVIEW PAPER Maladaptation and phenotypic mismatch in hatchery-reared Atlantic salmon Salmo salar released in the wild

fry kept as controls in captivity and those released and subsequently recapturedin the wild according to a before-after-control-impact (BACI) design. Hatchery fish that survived inthe wild became more cryptic and displayed a much lower incidence of fin erosion and of asymmetricindividuals than control fish kept in captivity. Significant differences in body shape were also apparent,and survivors had longer heads, thicker caudal peduncles and a more streamlined body shape thanhatchery controls as early as 20 days following stocking, most likely as a result of phenotypic plasticityandnon-random,selectivemortalityofmaladaptedphenotypes.Hatchery-rearedfishtypicallyperformpoorly in the wild and the results of this study indicate that this may be due to phenotypic mismatch,