Spawning migration and habitat, use of adfluvial brown trout, Salmo trutta, in a strongly seasonal boreal river

In July 2003, twenty large brown trout (Salmo trutta) were radio-tagged at Kiutakongas Falls in the Oulankajoki - a river in northern Finland - on their migration to spawning areas, to examine their movements, habitat use and overwintering in the river. The estimated average minimum daily movement of the trout before spawning was 348 m (S.D. = 139 m, n = 20), and during spawning, in late September, 208 m (S.D. = 160 m, n = 15). In winter, the fish were relatively localized (average minimum daily movement = 53 m, S.D = 23 m, n = 12). Upstream migrating trout ranged either in large, deep pool sections of the river or in rapid sections. During spawning, fish were commonly found in rapids and pool-rapid transition zones. In winter, trout resided almost entirely in deep pool sections. In spring, just after the ice break-up and rising water level due to snow melt, overwintering fish migrated downstream within two weeks, moving on average 2062 m (S.D. = 3514 m, n = 11) per day.