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Using bioenergetics and stable isotopes to assess the trophic role of rusty crayfish (Orconectes rusticus) in lake littoral zones

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Crayfish often dominate freshwater ecosystems and can have strong effects on littoral habitat and biota through foraging. However, there is substantial debate regarding the trophic role of crayfish and implications of their foraging behavior on littoral ecosystems. We created a bioenergetics model for rusty crayfish (Orconectes rusticus) to determine how growth and prey choice constrain crayfish consumption, which affects littoral ecosystems. We simulated over 6400 potential rusty crayfish diets by varying the abundance of important prey. We judged how crayfish prey choice affects the amount and identity of prey that crayfish must consume to match observed growth. We compared our model predictions with stable isotope evidence from 10 northern Wisconsin lakes to determine energy sources and trophic position of rusty crayfish relative to other invertebrates. Our diet simulations and stable isotope analysis concurred that crayfish of all ages are primarily predators. Individuals that do not feed on zoobenthos must therefore consume large quantities of less desirable food such as macrophytes, which are an important component of littoral habitat.

Les écrevisses dominent souvent les écosystèmes d'eau douce et peuvent, par leur recherche de nourriture, avoir de profonds effets sur l'habitat littoral et les organismes qui y vivent. Cependant, il existe un important débat sur le rôle trophique des écrevisses et les conséquences de leur comportent de recherche de nourriture sur les écosystèmes littoraux. Nous avons mis au point un modèle bioénergétique pour l'écrevisse américaine (Orconectes rusticus) afin de déterminer comment la croissance et le choix des proies limitent la consommation des écrevisses, ce qui affecte les écosystèmes littoraux. Nous avons fait des simulations impliquant plus de 6400 régimes alimentaires potentiels d'écrevisses en faisant varier l'abondance des proies principales. Nous avons déterminé comment le choix des proies par les écrevisses affecte le nombre et l'identité des proies que l'écrevisse doit consommer pour expliquer la croissance observée. Nous avons comparé les prédictions de notre modèle et les données d'analyse des isotopes stables provenant de 10 lacs du nord du Wisconsin afin de déterminer les sources d'énergie et la position trophique de l'écrevisse américaine par rapport aux autres invertébrés. Nos simulations de régimes alimentaires et l'analyse des isotopes stables s'accordent pour trouver que les écrevisses de tous les âges sont principalement des prédateurs. Les individus qui ne se nourrissent pas de zoobenthos doivent consommer de grandes quantités de nourriture moins désirable, telle que les macrophytes qui forment un compartiment relativement important de l'habitat littoral.

Document Type: Research Article

Publication date: February 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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