Aquatic invertebrates and waterbirds of wetlands and rivers of the southern Carnarvon Basin, Western Australia

Fifly-si\ sites, representing 53 wetlands, were suiveyed in the southem Camarvon Basin in 1994 and 1995 with the aim of documentine the waterbird and aquatic inverteblate fauna of the region. Most sites ivere surveyed in both winter and summer, although some contained water only one occasion. Altogether 57 waterbird species wete recorded, with 29 292 waterbirds of 25 species on Lake Macleod in October 1994. River pools were shown to be relatively important for waterbirds, while many ?reshwater .lavpans were l itt le used. Ai least 492 species of aquatic invertebrate were collected. The invedebrate fauna was charactedzed by the low ftequency with which taxa occurred: a third of the species wete collected at i single site on only one occasion. Patterns of occurence were not strongly seasonal. Many undescribed species were found and many range extensions were recotded, reflecting lick of previous aquatic inveltebrate work in the region. The level of regional endemicity could not be assessed adequately, although it is probably comparatively low. In terms of their invertebrate fauna, Iive types of wetlands were distinguished: river pools,_ rock pools and larger flowintstreams; seeps, springs and smaller cteeks; freshwater claypans; birridas; and Lake Macleod. Environmental factors to which invertebrates appeared to respond were ratio of calcium/ alkalinitr lotal dissolved solids, turbidity, colour, flow, longitude and nutrientt although some factors were inter-corelated. Additional surveyi should find extra species of waterbird and, mote particularly, aquatic invertebrate using wetlands of the southern Calnarvon Basin. For many invertebrates, occultences are too sparse for eflective protection of species within a nature resetve system and other mechanisms will be required to ensute their conservation. Comparison of site classifications based on waterbird, aquatic invertebrate and Dlant data (Gibson ei al., 2000) showed pattems among sites identified using one element of Lhe biota djd not refle.t patterns shown by other element". ihi. .uggests that, until further work hal identified an element that reflects the iviole wetland communitt as many biotic elements as possible should be surveyed. INTRODUCTION The southem Camarvon Basin is located on the mid-west coast of Westem Australia, in arr area with arid or semi-arid climate. The resion contains few nature reserves or nafiondl parkq although Shark Bay, in the centre of the regiorL is a World Heritage area (Anonymous 1995). In 1994, Environment Australia commissioned a comprehensive biological survey of the Basin, including its yegetation, marrunals, birds, amphibians, tenestrial arthr:opods and aquatic fauna (Burbidge ef al., 2000). Beginning with the extensive records of Tom Carter, many casual observations have been made of waterbirds in the southern Camarvon Basin and a number of small surveys undertaken flohlstone et al., 2000). Despite waterbirds probably being the most studied faunal group in the Basin, these historical data reveal only broad patterns of waterbird occurrence and some of the more important wetlands for waterbirds. They do not allow easy comparison of different wetlands. For aquatic invertebrates, even broad patterns of S.A. Hal6e, R.J. Shiel, A.W. Storey, D.H.D. Edward, I. Lansbury, D.J. Cale, M.S. Hawey Figure I Map of the survey area and boundary of the southern Carnarvon Basir; showing the distribution of the aquatic sampling sites and places mentioned in text. See Appendix 1 {or site codes. I l 5 '