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Juvenile coho salmon (Oncorhynchus kisutch) responses to salmon carcasses and in-stream wood manipulations during winter and spring

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Abstract:

We investigated the growth rate, winter survival, presmolt size, and emigration timing of juvenile coho salmon (Oncorhynchus kisutch) in response to salmon carcasses and in-stream wood. Experimental trials were conducted during two consecutive years and pre-winter fish size and densities differed between years. Sixteen pens with emigration traps were built in a side-channel of the Mamquam River, British Columbia. Pens were randomly assigned salmon carcasses, in-stream wood, both carcasses and in-stream wood, or neither (control). Our first trial was conducted between December 1996 and August 1997 and the second between December 1997 and August 1998. Initial rearing densities and average individual body mass were 3.1 fish·m–2 and 2.4 g, respectively, in the first trial and were 1.6 fish·m–2 and 6.6 g, respectively, in the second trial. Results were influenced by both fish initial size and density. During the first trial (smaller-sized fish at high densities), salmon carcasses increased fish growth rates and presmolt size. Winter survival did not increase in response to any treatment; however, a pre-winter size-related survival pattern was observed during the first trial. During the second trial, (larger-sized fish at low densities), no treatment influenced fish growth rates or presmolt size but all treatments augmented fish survival.

Nous avons étudié le taux de croissance, la survie à l'hiver, la taille avant la transformation en saumoneau et le calendrier de l'émigration chez de jeunes saumons coho (Oncorhynchus kisutch) en réaction à la présence de carcasses de saumons et de débris ligneux dans le cours d'eau. Nous avons fait des essais expérimentaux au cours de 2 années consécutives : les tailles des poissons avant l'hiver et leurs densités différaient d'une année à l'autre. Nous avons construit 16 enclos munis de pièges d'émigration dans un chenal latéral de la Mamquam, Colombie-Britannique. Nous avons placé dans les enclos de manière aléatoire des carcasses de saumons, des débris ligneux, à la fois des carcasses et du bois ou alors aucun ajout (témoins). Notre premier essai a eu lieu de décembre 1996 à août 1997 et le second de décembre 1997 à août 1998. La densité initiale d'élevage était de 3,1 poissons·m–2 et la masse individuelle moyenne du corps de 2,4 g dans le premier essai et respectivement de 1,6 poisson·m–2 et de 6,6 g dans le second essai. Les résultats sont influencés à la fois par la taille initiale et la densité des poissons. Durant le premier essai (poissons plus petits à forte densité), les carcasses de saumons augmentent les taux de croissance des poissons et leur taille avant la transformation en saumoneaux. La survie à l'hiver n'augmente dans aucune des situations expérimentales : on observe cependant dans le premier essai un patron de survie relié à la taille des poissons avant l'hiver. Durant le second essai (poissons plus grands à densité faible), aucune des conditions expérimentales n'influence les taux de croissance des poissons, ni leur taille avant la transformation en saumoneaux, mais toutes les conditions augmentent la survie des poissons.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: February 1, 2007

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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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