SPATIAL-DISTRIBUTION OF LITTORAL INVERTEBRATES IN THE LOWER MURRAY-DARLING RIVER SYSTEM, AUSTRALIA

The abundance and richness of macroinvertebrates in the lower Murray a nd Darling rivers were examined at a macroscale (rivers), mesoscale (b illabongs, backwaters, channel) and microscale (vegetation, snags, sub strata). In the Darling, insects dominated (85% of taxa, 81% of indivi duals); the richest taxa were Diptera (26 taxa) and Coleoptera (15 tax a) and the most abundant were Hemiptera (47%) and Diptera (35%). In th e Murray, insects again dominated (84% of taxa, 52% of individuals), p articularly Diptera (22 taxa), Coleoptera (12 taxa) and Hemiptera (9 t axa), but there were more crustaceans (9% of taxa, 47% of individuals, particularly the atyid shrimp Paratya australiensis). Both assemblage s were uneven: in the Darling, >50% of biomass was Micronecta spp. (Co rixidae), Dicrotendipes sp. (Chironomidae) and Macrobrachium australie nse (Palaemonidae); in the Murray, 70% of biomass was P. australiensis and Caridina mccullochi (Atyidae) and the insects Micronecta spp. (Co rixidae) and Chironomus sp. (Chironomidae). Abundances generally were greatest in the Murray. Hydrologic and geomorphic factors influenced a ssemblages at the macroscale, whereas microhabitat diversity dominated at the mesoscale.