Trophic Niche Segregation in the Nilotic Ichthyofauna of Lake Albert (Uganda, Africa) |
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Authors: | Linda M. Campbell Sylvester B. Wandera Robert J. Thacker D. George Dixon Robert E. Hecky |
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Affiliation: | (1) Department of Biology, University of Waterloo, 200 University Avenue, Waterloo, Ontario, N2L 3G1, Canada;(2) Fisheries Resources Research Institute, P.O. Box 343, Jinja, Uganda;(3) Department of Physics and Astronomy, McMaster University, 1280 Main St, W, Hamilton, Ontario, Canada;(4) Present address: School of Environmental Studies and Department of Biology, Queen’s University, K7L 3N6, Kingston, ON, Canada;(5) Present address: Department of Physics and Astronomy, Queen’s University, K7L 3N6, Kingston, ON, Canada |
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Abstract: | Synopsis Nile perch, Lates niloticus, and Nile tilapia, Oreochromis niloticus, were originally transplanted from Lake Albert in western Uganda to the African Great Lakes, Lake Victoria and Lake Kyoga, where they are partially implicated in reduction of the fish species diversity. Lake Albert is facing multiple environmental changes, including declining fish species diversity, hyper-eutrophication, hypoxia, and reduced fish catches. To examine the role of Nile perch and Nile tilapia in the food web in their native Lake Albert, we estimated their diets using stable nitrogen and carbon isotopes. In Lake Albert, the tilapiine congeners (closely related species), Tilapia zillii, Oreochromis leucostictus, and Sarethorodon galilaeus, and the centropomid Nile perch congener, Lates macrophthalmus, have narrower diet breath in the presence of the native O. niloticus and L. niloticus. A computerized parameter search of dietary items for five commercially important fish species (Hydrocynus forskahlii, Bagrus bayad, L. niloticus, Alestes baremose and Brycinus nurse) was completed using a static isotopic mixing model. The outcome of the simulation for most fish species compared favorably to previously published stomach contents data for the Lake Albert fishes dating back to 1928, demonstrating agreement between stable isotope values and analyses of stomach contents. While there were some indications of changes in the diets of L. niloticus and A. baremose diets over the past 20 years in parallel with other changes in the lake, for the most part, food web structure in this lake remained stable since 1928. The Lake Albert fish assemblage provides insight into the invasion success of L. niloticus and O. niloticus. |
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Keywords: | δ 13C δ 15N food webs Nile perch stable isotopes |
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