title: Silver spoons in the rough: can environmental enrichment improve survival of hatchery Atlantic salmon Salmo salar in the wild?
abstract: This study tested the 'silver spoon' hypothesis which posits that individuals that develop under favourable conditions should enjoy a fitness advantage later in life because they are more likely to recognize and settle in high-quality habitats. Atlantic salmon Salmo salar of two age classes (0+ and 1+ years) were reared in environmentally enriched or standard hatchery tanks for a short period (c. 10 weeks), were then released into a natural river and sampled on repeated occasions to test for silver-spoon effects. Compared with controls, enriched fish had a 6.4% higher recapture rate and settled in higher velocity habitats when they were stocked as 0+ year fry, but not when they were stocked as 1+ year parr. The opportunity for selection was generally higher for environmentally enriched fish than for controls, and also higher for 0+ than for 1+ year fish. Selection favoured individuals with high condition factor, extensive fat reserves and longer than average pectoral fins in both age classes but favoured a small body size in 1+ year and a large body size in 0+ year releases. Stomach analysis showed that enriched fish ate more, and adapted quicker to natural prey than controls. These results provide support for silver-spoon effects in fish and indicate that enrichment can improve post-release performance in conservation programmes, but seemingly only if fish are not kept in captivity for too long.
authors.affiliation: Swansea University, Centre for Sustainable Aquatic Research, Department of Biosciences, Swansea SA2 8PP, U.K.
authors.forename: L J
authors.initials: LJ
authors.lastname: Roberts
authors.forename: J
authors.initials: J
authors.lastname: Taylor
authors.forename: P J
authors.initials: PJ
authors.lastname: Gough
authors.forename: D W
authors.initials: DW
authors.lastname: Forman
authors.forename: C
authors.initials: C
authors.lastname: Garcia de Leaniz
mesh_terms: D000818:Animals; D017756:Aquaculture / Q000379:methods*; D004777:Environment; D010641:Phenotype; D020317:Salmo salar / Q000033:anatomy & histology / Q000502:physiology*; D012641:Selection, Genetic
keywords: domestication; feralization; fitness; hatcheries; salmonids; selection