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The influence of food quality and availability on trophic position, carbon signature, and growth rate of an omnivorous crayfish

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Fourteen sites in 13 streams were surveyed to address the importance of food quality and quantity on trophic position, carbon signature, and growth rate of noble crayfish (Astacus astacus) by combining the analyses of gut content, stable isotopes, and RNA–DNA ratio. The gut content analysis showed an omnivorous feeding habit, but total animal food sources contributed more to the nitrogen and carbon isotope signals of this species. The biomass of invertebrates (i.e., high quality food) influenced the trophic position, carbon signature, and growth rate. Our results show that crayfish in streams with a high biomass of invertebrates were at a higher trophic position and had a higher growth rate than crayfish in streams with a low biomass of invertebrates. A high biomass of relatively sedentary invertebrates indicates a habitat with high algae biomass, which is reflected in the more autochthonous carbon signature of crayfish. Further, noble crayfish in temperate streams seem to have dual functional roles by acting as predator and as shredder by processing large amounts of detritus.

Nous avons inventorié 14 sites dans 13 cours d’eau pour déterminer l’importance de la qualité et la quantité de la nourriture sur la position trophique, la signature de carbone et le taux de croissance de l’écrevisse à pattes rouges (Astacus astacus) en combinant des analyses du contenu du tube digestif, des isotopes stables et des rapports ARN–ADN. L’analyse du contenu du tube digestif révèle des habitudes alimentaires d’omnivore, mais l’ensemble des sources alimentaires animales contribuent plus aux signaux isotopiques d’azote et de carbone chez cette espèce. La biomasse des invertébrés (c’est-à-dire de la nourriture de haute qualité) influence la position trophique, la signature de carbone et le taux de croissance. Nos résultats montrent que les écrevisses dans les cours d’eau à forte biomasse d’invertébrés occupent une position trophique supérieure et ont un taux de croissance plus élevé que les écrevisses dans les cours d’eau à faible biomasse d’invertébrés. Une importante biomasse d’invertébrés relativement sédentaires représente un habitat avec une forte biomasse d’algues, ce qui se reflète dans la signature de carbone plus autochtone des écrevisses. De plus, l’écrevisse à pattes rouges dans les cours d’eau tempérés semble jouer deux rôles fonctionnels, en agissant comme prédateur et aussi comme déchiqueteur responsable du traitement de grandes quantités de détritus.

Document Type: Research Article

Publication date: October 1, 2008

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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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