Spatial and Temporal Patterns in Fish Assemblages Following an Artificially Extended Floodplain Inundation Event, Northern Murray-Darling Basin, Australia |
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Authors: | Robert J Rolls G Glenn Wilson |
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Institution: | (1) Ecosystem Management, University of New England, Armidale, NSW, 2351, Australia;(2) Present address: Australian Rivers Institute, Griffith University, Nathan, QLD, 4111, Australia |
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Abstract: | Water extraction from dryland rivers is often associated with declines in the health of river and floodplain ecosystems due
to reduced flooding frequency and extent of floodplain inundation. Following moderate flooding in early 2008 in the Narran
River, Murray-Darling Basin, Australia, 10,423 ML of water was purchased from agricultural water users and delivered to the
river to prolong inundation of its terminal lake system to improve the recruitment success of colonial waterbirds that had
started breeding in response to the initial flooding. This study examined the spatial and temporal patterns of fish assemblages
in river and floodplain habitats over eight months following flooding to assess the possible ecological benefits of flood
extension. Although the abundances of most fish species were greater in river channel habitats, the fish assemblage used floodplain
habitats when inundated. Young-of-the-year (4–12 months age) golden perch (Macquaria ambigua) and bony bream (Nematalosa erebi) were consistently sampled in floodplain sites when inundated, suggesting that the floodplain provides rearing habitat for
these species. Significant differences in the abundances of fish populations between reaches upstream and downstream of a
weir in the main river channel indicates that the effectiveness of the environmental water release was limited by restricted
connectivity within the broader catchment. Although the seasonal timing of flood extension may have coincided with sub-optimal
primary production, the use of the environmental water purchase is likely to have promoted recruitment of fish populations
by providing greater access to floodplain nursery habitats, thereby improving the ability to persist during years of little
or no flow. |
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