Preliminary trophic network analysis of subalpine Lake Annecy (France) using an Ecopath model

• Main Authors: D. Gerdeaux, M.Y. Janjua
• Format: Article
• Language: English
• Published: EDP Sciences 2009-05-01
• Series: Knowledge and Management of Aquatic Ecosystems
• Subjects: trophic model; Ecopath; Lake Annecy; fisheries
• Online Access: http://www.kmae-journal.org/index.php?option=article&access=standard&Itemid=129&url=/articles/kmae/pdf/2009/01/kmae09001.pdf

Lake Annecy is the second largest natural lake in France, with intensive commercial and recreational fisheries. However, there is limited knowledge of its trophic interaction. A preliminary Ecopath model was fitted to study the trophic interaction in the lake using the available data on most of the ecosystem compartments. Fourteen functional groups were used in the present analysis. Most of the consumers have ecotrophic efficiency from 0.3 to 0.6. The results show that flow from detritus is as important as flow from primary producers. The overall transfer efficiency of the system is 9.6. The primary production/respiration (Pp/R) ratio, which is 3.253, shows that Lake Annecy's ecosystem is comparatively mature. The gross efficiency of fisheries is 0.001173. Catch trophic level and percentage of primary productivity required for catch show that fishery in Lake Annecy is stable. The values of ascendancy (31.2) and overhead (68.8) show the stability of the ecosystem. Mixed trophic analysis indicates that zoobenthos have a positive effect on most of the fish functional groups. This preliminary model can be helpful to pinpoint the gaps in the present knowledge about Lake Annecy.