Aquaculture and Fisheries Management 1989, 20, 475-484 Survival, exploitation and movement of takeable size brown trout, Salmo trutta L., in a Norwegian river T. HESTHAGEN & B. JONSSON Fish Research Division, Norwegian Institute for Nature Research, Trondheim, Norway J. SKVRDAh Environmental Division, Statsetatenes Hits, Lillehammer, Norway Abstract. Takcable-sized (25-61 cm total length), hatchery-reared brown trout, Salmo trutta L., were released in early July from 1982 to 1984 in the sub-alpine River Sjoa in southern central Norway. Of those recovered during the same season that they were stocked, 67-73% were caught within 10 days. Mean exploitation and survival rates in the same season of release ranged from 0 41 to 0-54 and 005 to O i l , respectively. No tagged fish were caught 2 years after stocking. The frequency of capture increased significantly with fish length. The length at stocking of those fish recovered after one winter in the river was greater than those caught in the same season as released. The migrant fish {n = 20) were significantly larger than stationary fish (n = 434). Between 87-5 and 95-6% of thefishwith known capture sites caught during the first year (n = 180) were recovered in the release area. The highest fraction of migrants was obtained in the year with the highest stocking density; the water discharge was also higher that year. The migrants (n = 17) were caught 1 0-6-Okm downstream, with the exception of one fish which moved 2-0 km upstream. The year after stocking, 63% {n = 8) ofthe remainder were caught in the release area, while the migrants {n = 3) were caught 2-0-6-0km downstream. Introduction Angling for brown trout, Salmo trutta L., in inland rivers is the most important recreational fishery in Norway (Anon. 1983). This fishery involves about 1 million inhabitants (the total population of Norway is 4-1 million) as well as a large number of foreign tourists. However, the demand for sport fishing cannot always be met by wild fish populations. Stocking of hatchery reared takeable-sized brown trout has therefore been carried out during recent years, although this is not yet a common practice (Aass 1978, 1981). The takeable-sized trout used in such releases usually originate from lake-living populations. For management purposes, it is important that the stocked fish become resident in the area of their release. However, this is not always the case, asfishfrom different stocks exhibit different migration tendencies (Jonsson 1982, 1985; Svardson & Fagerstr0m 1982). Further, strain domestication may also affect characteristics such as catchability, movement direction and survival rate (Brauhn & Kincaid 1982; Dwyer & Piper 1984; Fay & Pardue 1986). Most recoveries of trout stocked at takeable size in streams seem to be made close to the point of their release within a short period after release (Mills & Ryan 1973; Cresswell 1981; Correspondence: Dr T. Hesthagen, Fish Research Division, Norwegian Institute for Nature Research, Tungasletta 2, N-7004 Trondheim, Norway. 41S