CYTOGENETICAL CHARACTERIZATION OF HATCHERY STOCKS AND NATURAL-POPULATIONS OF SEA AND BROWN TROUT FROM NORTHWESTERN SPAIN

A karyotypic analysis was carried out using conventional staining and banding techniques in Brown Trout and Sea Trout. An important variation in the number of chromosome arms (NF), but not in chromosome number was demonstrated. This wide polymorphism is due essentially to the variation in the short arm of the Nuclear Organizer Region (NOR)-bearing chromosome number 11, which can be used as a population marker. Duplications and triplications of the NOR region are responsible for this variation. The number of NORs per genome are also variable between individuals in a high frequency. C-band polymorphism of the short arms of chromosome pairs 8 and 9 was also demonstrated.