Macroinvertebrate sampling methods for lowland Australian rivers

The macroinvertebrate communities of large lowlandrivers are little studied, partly because of the lackof suitable collection methods. In this study, fourmacroinvertebrate collecting methods: two artificialsubstrates, snags and onion-bag baskets; air-liftsampling of soft sediments; and sweep net sampling ofedges (including macrophyte stands where theyoccurred) were trialed in four lowland rivers withinthe Murray-Darling Basin in southeastern Australia. The subset of the macroinvertebrate communitycollected by each method was determined and the numberof replicates needed for a given degree of precisionwas estimated. Sweep samples were dominated byhemipterans and were the best method for collectingdecapods and beetles. The other three methodscollected mostly chironomid, caenid mayfly and ecnomidcaddisfly larvae and oligochaetes. The artificialsnag and basket samples had surprisingly similarcompositions but the snag samples did contain sometaxa, such as Dicrotendipes, Paratanytarsus andwood-boring beetles, that basket samples did not. Thedensities of macroinvertebrates collected byartificial snags, sweep and air-lift samples weresimilar. We concluded that each of the methods couldbe used in lowland rivers but for different purposes. For example, if quantitative data are needed, onlyair-lifts and snags would be appropriate, whereas ifa species list is required, snags and sweeps would bemost effective.