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The influence of prey availability on ontogenetic diet shifts of a juvenile piscivore

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Abstract:

Young-of-year piscivores typically undergo ontogenetic diet shifts from planktivory to benthivory to piscivory. These shifts are often the result of changes in predator foraging abilities, but little is known about the influence of relative prey availability. As a result, we examined diet shifts across a range of sizes (20–150 mm) of a young-of-year piscivore, walleye (Sander vitreus), in feeding experiments in which zooplankton, benthic invertebrates, and fish were made available at different density combinations. Consumption of each prey type changed with walleye size and prey densities. Small juveniles (20 mm) selected zooplankton and fish, whereas larger walleye (40–100 mm) selected benthic invertebrates and fish. Relative prey densities influenced consumption; increased densities of more profitable prey types resulted in reduced consumption of less profitable prey. Walleye larger than 100 mm selected only fish. Foraging efficiencies also varied with size and prey types; small walleye (20 mm) were less likely to pursue benthic invertebrates and retain captured fish. These ontogenetic changes in foraging patterns are linked to prey profitability, have growth consequences for juvenile walleye, and have implications for understanding diet shifts of other juvenile fish.

Durant leur première année, les piscivores subissent typiquement des changements de régime alimentaire qui passe de la planctonophagie à la benthophagie à l'ichtyophagie. Ces changements sont souvent le résultat de modifications dans les capacités de recherche de nourriture du prédateur, mais on sait peu de choses sur l'effet de la disponibilité des proies. Nous avons donc étudié les changements de régime alimentaire chez des jeunes piscivores de l'année, soit des dorés (Sander vitreus) de tailles variées (20–150 mm), dans des expériences d'alimentation dans lesquelles du zooplancton, des invertébrés benthiques et des poissons étaient disponibles en diverses combinaisons de densité. La consommation de chaque type de proie varie en fonction de la taille des dorés et de la densité des proies. Les jeunes de petite taille (20 mm) choisissent du zooplancton et des poissons, alors que les dorés plus grands (40–100 mm) sélectionnent des invertébrés benthiques et des poissons. Les densités relatives des proies influencent la consommation; des densités accrues de types de proies plus avantageuses causent une réduction de la consommation de proies moins profitables. Les dorés de taille supérieure à 100 mm choisissent seulement des poissons. L'efficacité de l'alimentation varie aussi en fonction des tailles des poissons et des types de proies; les petits dorés (20 mm) sont moins susceptibles de pourchasser les invertébrés benthiques et de retenir les poissons qu'ils capturent. Ces changements ontogéniques dans les patrons alimentaires sont reliés aux bénéfices associés aux proies, ils ont des conséquences sur la croissance des jeunes dorés et ils ont des implications sur notre compréhension des changements alimentaires chez d'autres jeunes poissons.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: August 1, 2006

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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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