Biodiversity on the brink: an assessment of conservation strategies for North American freshwater mussels |
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Authors: | Wendell R Haag James D Williams |
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Institution: | 1. Netherlands Institute of Ecology (NIOO-KNAW), Droevendaalsesteeg 10, 6708 PB, Wageningen, The Netherlands 2. Amhara Region Agricultural Research Institute, P.O. Box 527, Bahir Dar, Ethiopia 3. FAO, Sub Regional Office for Eastern Africa, P.O. Box 5536, Addis Ababa, Ethiopia 4. Department of Zoological Sciences, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia 5. Aquaculture and Fisheries Group, Wageningen Institute of Animal Sciences (WIAS), Wageningen University, De Elst 1, 6708 WD, Wageningen, The Netherlands
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Abstract: | Fish and zooplankton populations of nine Ethiopian freshwater lakes were quantitatively sampled along a North–South gradient. Differences in altitude and latitude resulted in a temperature gradient from North to South. We tested three hypotheses: (1) the degree of zooplanktivory decreases with water temperature, i.e. from North to South; (2) the degree of zooplanktivory increases with the abundance of large-bodied zooplankton; and (3) the pattern of zooplanktivory in eutrophic Ethiopian water bodies differs from other tropical and temperate water bodies. Proportions of zooplanktivory in the fish communities did not show a geographical trend, but mainly depended on fish species, zooplankton density and the availability of large-bodied cladocerans. The degree of zooplanktivory in eutrophic Ethiopian water bodies differs from other eutrophic water bodies, both temperate and tropical. In Ethiopia, the degree of zooplanktivory can be both low and high, in contrast with other tropical water bodies where zooplanktivory is generally low and with temperate eutrophic water bodies where it is generally high. As a result, predation pressure on zooplankton by fish varies dramatically amongst Ethiopian water bodies. |
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