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Reduced hatchery rearing density increases social dominance, postrelease growth, and survival in brown trout (Salmo trutta)

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Abstract:

Hatchery fish reared for conservation or supplementation often have difficulties adapting to natural conditions, resulting in poor performance in the wild. In a standard hatchery, fish are confined at high densities, which creates a social environment different from that experienced after release. Here we investigated how rearing density influences social dominance, postrelease growth, and survival in brown trout (Salmo trutta). Fish were reared at three density treatments: conventional hatchery density, half of conventional hatchery density, and natural density. Four months after hatching, dominance status was determined, and 36 fish from each treatment were released into an enclosed stream and recaptured after 36days. Trout reared at natural density had higher dominance status and grew faster, both in the hatchery and in the natural stream, than trout from higher densities. Moreover, trout reared at natural density were twice as likely to survive in the stream as trout from higher densities. These novel results suggest that more natural rearing densities would facilitate the development of adaptive behaviour in hatchery salmonids and, thereby, their contribution to natural production.

Les poissons élevés en pisciculture pour la conservation ou la supplémentation ont souvent de la difficulté à s’adapter aux conditions naturelles, ce qui entraîne une performance mitigée en nature. Dans une pisciculture ordinaire, les poissons sont confinés à des densités élevées, ce qui crée un environnement social différent de celui qu’ils connaissent après leur libération. Nous étudions comment la densité durant l’élevage influence la dominance sociale, la croissance après la libération et la survie chez la truite brune (Salmo trutta). Nous avons élevé des poissons dans trois conditions expérimentales, la densité habituelle de pisciculture, une densité de moitié de la densité habituelle de pisciculture et la densité naturelle. Quatre mois après l’éclosion, nous avons déterminé le statut de dominance et libéré 36 poissons de chacun des traitements dans un cours d’eau fermé pour les capturer 36 jours plus tard. Les truites élevées à des densités naturelles ont un statut de dominance supérieur et croissent plus rapidement, tant en pisciculture que dans le cours d’eau naturel, que les truites gardées aux densités plus élevées. De plus, les truites élevées aux densités naturelles sont deux fois plus susceptibles de survivre dans le cours d’eau que les truites élevées aux densités plus fortes. Ces résultats inédits indiquent que des densités d’élevage plus naturelles favoriseraient le développement d’un comportement adaptatif chez les salmonidés d’élevage et, par conséquent, amélioreraient leur contribution à la production naturelle.

Document Type: Research Article

Publication date: 2010-02-01

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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