Spatial variation in composition and richness of fish communities in a southwestern Australian river system |
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Authors: | Michael J Hutchison |
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Institution: | (1) Department of Geography, University of Western Australia, 6009 Nedlands, Western Australia, Australia |
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Abstract: | Thirteen species of fish were recorded from the non-tidal reaches of the Murray River system, southwestern Australia. Of these,
nine were indigenous species. Although this system occurs in a zone of moderate to high rainfall, the species richness of
this system is comparable to that of much harsher environments, such as the Canadian boreal zone or the Nevada desert. Species
richness tends to increase in a downstream direction, and most changes in species composition are due to addition, rather
than replacement of species. Stream order was strongly and significantly positively correlated with species richness (P < 0.001), but was in effect functioning as a composite variable. Stepwise multiple regression analysis showed that stream
width, pH range, distance from the main stream, distance from the estuary, barriers and stream gradient together explained
more than 80% of the variation in species richness. The variables, barriers, distance from the main stream and distance from
the estuary, support island biogeography type explanations for variations in species richness, while the variable, stream
width complies with the river continuum concept. A predictive model for species richness of any given reach of a lower west
coastal stream in Australia was tried using variables that can be gathered almost entirely from detailed topographic maps
and aerial photographs. |
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Keywords: | biogeography fishes predictive model southwestern Australia species richness |
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