title: Passing a seawater challenge test is not indicative of hatchery-reared Atlantic salmon Salmo salar smolts performing as well at sea as their naturally produced conspecifics.
abstract: Despite satisfactory reactions to seawater challenge tests indicative of appropriate physiological state, hatchery-reared Atlantic salmon Salmo salar smolts stocked in the Eira River in Norway between 2001 and 2011 performed less well at sea in terms of growth, age at maturity and survival than smolts of natural origin. The mean rates of return to the river for hatchery-reared and naturally produced S. salar were 0·98 and 2·35%. In the Eira River, c. 50 000 hatchery-reared S. salar smolts of local origin were stocked annually to compensate for reduced natural smolt production following regulation for hydroelectric purposes, while a mean of 17 262 smolts were produced naturally in the river. This study demonstrates that, although captive S. salar perform well in seawater challenge tests, hatchery-reared smolts are not necessarily as adaptable to marine life as their naturally produced counterparts. These findings suggest that production of hatchery-reared smolts more similar to naturally produced individuals in morphology, physiology and behaviour will be necessary to improve success of hatchery releases. Where possible, supplementary or alternative measures, including habitat restoration, could be implemented to ensure the long-term viability of wild stocks.
authors.affiliation: Norwegian Institute for Nature Research (NINA), P. O. Box 5685 Sluppen, NO-7485, Trondheim, Norway.
authors.forename: A J
authors.initials: AJ
authors.lastname: Jensen
authors.affiliation: Norwegian Institute for Nature Research (NINA), P. O. Box 5685 Sluppen, NO-7485, Trondheim, Norway.
authors.forename: M
authors.initials: M
authors.lastname: Berg
authors.affiliation: Norwegian Institute for Nature Research (NINA), P. O. Box 5685 Sluppen, NO-7485, Trondheim, Norway.
authors.forename: G
authors.initials: G
authors.lastname: Bremset
authors.affiliation: Norwegian Institute for Nature Research (NINA), P. O. Box 5685 Sluppen, NO-7485, Trondheim, Norway.
authors.forename: B
authors.initials: B
authors.lastname: Finstad
authors.affiliation: Norwegian Institute for Nature Research (NINA), P. O. Box 5685 Sluppen, NO-7485, Trondheim, Norway.
authors.forename: N A
authors.initials: NA
authors.lastname: Hvidsten
authors.affiliation: Norwegian Institute for Nature Research (NINA), P. O. Box 5685 Sluppen, NO-7485, Trondheim, Norway.
authors.forename: J G
authors.initials: JG
authors.lastname: Jensås
authors.affiliation: Norwegian Institute for Nature Research (NINA), P. O. Box 5685 Sluppen, NO-7485, Trondheim, Norway.
authors.forename: B O
authors.initials: BO
authors.lastname: Johnsen
authors.affiliation: Faktor AS, Malvikveien 426, NO-7563, Malvik, Norway.
authors.forename: E
authors.initials: E
authors.lastname: Lund
mesh_terms: D000818:Animals; D001688:Biological Products; D005398:Fisheries; D009664:Norway; D045483:Rivers; D020317:Salmo salar / Q000502:physiology*; D012623:Seawater
chemical_list: D001688:Biological Products
keywords: adaptability; hypo-osmoregulatory evaluation; marine growth, sea survival; smolt  production