Migrations of soufie (Leuciscus souffia agassizii, VAL. 1844) in a natural river and a tributary determined by mark-recapture

From April to October 1998, soufie (Leuciscus souffia agassizii, VAL. 1844) were fished monthly using electrofishing at four sampling sites in the Argen River and in a little tributary. All fish with a body size exceeding 8 cm were tagged individually using micro tags. Additionally the fish were tagged according to sampling site by jet injection using Alcian Blue dye. The main part of the soufie population exhibited a migratory behaviour during the year between winter and summer habitat. Most of the soufie overwintered in a pool of a little tributary of the river, whereas age 0 + soufie remained in the river for the whole year. After spawning in spring in the river, the fish segregated during summer for feeding in the main river system. In the autumn, the fish returned to their winter habitat. It is concluded that the tributary plays an important role as overwintering habitat for the soufie population (except 0 +) of the investigated river section.