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Empirical evaluation of predator-driven diel vertical migration in Lake Superior

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Abstract:

Recent studies on Lake Superior suggest that diel vertical migration (DVM) of prey (generalized Coregonus spp.) may be influenced by the density of predatory siscowet (Salvelinus namaycush). We empirically evaluated this hypothesis using data from acoustic, midwater trawl, and bottom trawl sampling at eight Lake Superior sites during three seasons in 2005 and a subset of sites in 2006. We expected the larger-bodied cisco (Coregonus artedi) to exhibit a shallower DVM compared with the smaller-bodied kiyi (Coregonus kiyi). Although DVM of kiyi and cisco were consistent with expectations of DVM as a size-dependent, predator-mediated process, we found no relationship between siscowet density and the magnitude of DVM of either coregonid. Cisco appear to have a size refuge from siscowet predation. Kiyi and siscowet co-occur in demersal habitat> 150m during the day, where visual predation is unlikely, suggesting predator avoidance is not a factor in the daytime distribution of kiyi. Seasonal patterns of kiyi DVM were consistent with reported DVM of their primary prey Mysis relicta. Our results suggest that consideration of nonvisual foraging, rather than light-based foraging theory (i.e., the antipredation window), is necessary to understand the processes driving DVM in deepwater systems.

Des études récentes sur le lac Supérieur laissent croire que la migration verticale journalière (DVM) des proies (les Coregonus spp. en général) est influencée par la densité du prédateur, le touladi siscowet (Salvelinus namaycush). Nous évaluons cette hypothèse de manière empirique à l’aide de données provenant d’échantillonnages acoustiques et de prélèvements aux chaluts pélagique et benthique dans huit sites au lac Supérieur durant trois saisons en 2005 et dans un sous-ensemble de sites en 2006. Nous nous attendions à ce que le cisco de lac (Coregonus artedi) de plus grande taille ait une DVM moins profonde que le cisco kiyi (Coregonus kiyi) plus petit. Bien que les DVM du cisco kiyi et du cisco de lac soient en accord avec les attentes relatives à la DVM comme processus relié à la taille et géré par le prédateur, il n’existe aucune relation entre la densité du siscowet et l’importance de la DVM chez les deux corégonidés. Les ciscos semblent posséder un refuge relié à la taille contre la prédation du siscowet. Le cisco kiyi et le cisco de lac se retrouvent ensemble dans l’habitat benthique > 150 m durant le jour où la prédation visuelle est peu probable, ce qui indique que l’évitement des prédateurs n’est pas un facteur explicatif de la répartition du cisco kiyi durant la journée. Les patrons saisonniers de DVM du cisco kiyi correspondent aux patrons de DVM signalés chez leur proie principale Mysis relicta. Nos résultats indiquent qu’il faut tenir compte de la recherche non visuelle de nourriture plutôt que de la recherche basée sur la lumière (c’est-à-dire, la fenêtre antiprédation) pour comprendre les processus explicatifs de la DVM dans les systèmes d’eau profonde.

Document Type: Research Article

Publication date: March 1, 2010

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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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