DARLING RIVERINE PLAINS BIOREGION Background Report

16/08/02 Darling Riverine Plains Bioregion Background Report
6 OTHER FAUNA
6.1 INVERTEBRATES
Very little is known about invertebrate diversity within the bioregion. Not only is this
knowledge of importance for assessing the biodiversity of the area, but invertebrates also
perform an essential role in ecosystem function. They are of critical importance as food for
many species (such as bats, insectivorous birds, water birds, waders, dasyurids and reptiles)
and play an important role as decomposer organisms and in nutrient cycling. Some species
can also be agricultural pests. Due to the lack of information about invertebrates, it is not
possible to estimate rates of extinction or decline. As invertebrates play a critical role in the
functioning of natural systems, improving the information base and therefore the conservation
management for this group is critical to any strategy for conserving biodiversity (New 1984;
NPWS 1992). A list of invertebrate taxa recorded from the DRP is shown in Appendix G.
6.1.1 Aquatic invertebrates
Rivers and streams exist as a patchwork of habitats, which can be classified into three broad
habitat types for aquatic invertebrates. Macrohabitats are the large distinct reaches of the river
system; mesohabitats are smaller habitats including the main channel, backwaters, billabongs,
effluent creeks and floodplain channels; and microhabitats are the smallest habitat types
which include snags (fallen timber), aquatic vegetation and different substrate types.
In a survey of aquatic invertebrates in these three primary habitat types in the Darling River
between Bourke and Wilcannia, Sheldon (1995) found insects were the dominant group,
comprising 85% of taxa and 81% of individuals. Of these Dipterans (flies) and Coleopterons
(beetles) were most abundant. Billabongs had a greater number of taxa and individuals than
channel habitats and temporary billabongs had more individuals than permanent billabongs.
Overall, river geomorphology was found to significantly influence aquatic invertebrate
assemblages through the diversity of mesohabitats and microhabitats it supports. Flow
regulation also modifies the assemblage composition by favouring the development of
specific microhabitat and isolating mesohabitats (Sheldon 1995).
In the Macquarie Marshes a baseline survey of aquatic invertebrates found 197 taxa of which
85% were insects (65 Coleopteron taxa, 54 Dipterans, 24 Hemipterans). In general, cumbungi
swamps, lagoons, slow moving streams and intermittent streams had the greatest number of
taxa present (Bray 1994a). Cherax destructor (yabby), a common resident in the Marshes,
survives dry periods by burrowing into the mud.
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