Cranial trait differences between hatchery and wild fish of Eizenam brown trout and Atlantic salmon (Salmonidae)

Craniological traits were compared between hatchery-raised and wild-caught juveniles in the Eizenam brown trout Salmo trutta ezenami Berg, 1948 and the Atlantic salmon S. salar Linnaeus, 1758. Six out of ten meristic traits under study were found to differ significantly between the wild and cultivated samples in either species. Among 39 morphometric trait indices, 22 differed significantly between the S. trutta ezenami samples and 14, between the S. salar samples. Differences in meristic traits between the wild and hatchery samples of the same species were greater than differences between the two species. The differences were most likely determined by differences in environmental conditions, although an effect of size variation could not be excluded completely (cultivated fish were somewhat smaller than wild fish). High plasticity of craniological traits should be taken into account when studying the taxonomy and evolution of salmonids.