Stream fish assemblages in relation to environmental factors on a montane plateau (Nyika Plateau,Malawi) |
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Authors: | Wilbert T Kadye Christopher H D Magadza Ngonidzashe A G Moyo Shakkie Kativu |
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Institution: | (1) T.R.E.P., Department of Biological Sciences, University of Zimbabwe, Mount Pleasant, P.O. Box MP 167 Harare, Zimbabwe;(2) University of Limpopo, Aquaculture Research Unit, Private Bag X1106, Sovenga, 0727, South Africa |
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Abstract: | Few studies have examined river fishes of Malawi. This study is one of the first to examine the stream fish assemblages on
the Nyika Plateau in northern Malawi. Twenty four sites were sampled over three different periods in two river systems of
the plateau. Eighteen species were collected and among these was Hippopotamyrus ansorgii, the first collection of this species in the Lake Malawi catchment. Three species, including a non-native trout, were common
in the two systems studied. Correspondence analysis (CA) suggested gradients in species composition related to altitude and
river type. Species succession, from a trout dominated upstream to a downstream dominated by indigenous species, was shown
on the first CA axis. The second CA axis showed the assemblage of the plateau separated by river type. A direct gradient analysis
method, canonical correspondence analysis (CCA), showed the importance of two stream position metrics (stream order and c-link),
depth, water temperature and substrate type in determining species composition. According to variation partitioning in CCA,
the spatial and temporal components respectively explained 46% and 3.6% variation in assemblage composition based on the all
species data matrix, and 48.7% and 2.6% variation in assemblage composition based on the native species data matrix. The species
collected were also discussed in relation to the morphological adaptations in their body forms to the environmental conditions
of the streams studied. |
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Keywords: | Cyprinid Oncorhynchus mykiss Hippopotamyrus ansorgii Ordination Stream position metrics Local habitat variables |
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