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Hydrological connectivity in river systems facilitates the movement of animals across riverine landscapes and influences fish habitat but is threatened by climate change and water resource developments. We studied fish assemblages across a large wet–dry tropical river system in northern Australia that is under consideration for new agricultural and water resource developments, which are expected to alter hydrological connectivity. We explored relationships between the environment and several biotic variables; fish taxonomic composition, species turnover, and species trait presence, quantifying how they were related to hydrological connectivity. Environmental dissimilarity of sites was influenced by hydrological connectivity variables, including flow, elevation, and river distance. Environment characteristics and hydrological connectivity together were important predictors of fish taxonomic composition. Fish species turnover was highest in headwater sites, and species presence absence was related to feeding and reproductive traits. Our results suggest that habitat specialists and species with reproductive traits that depend on hydrological connectivity, such as diadromous species, are most vulnerable to declines in relative abundance following a reduction in connectivity, which would lead to range contractions within catchments. Maintaining habitats that support taxonomically and functionally unique fish assemblages, such as wetlands and headwater streams, is important for maintaining biodiversity. [ABSTRACT FROM AUTHOR]

Mining is an environmentally destructive human activity. Consequently, community expectations and legislation require minimisation of impacts and rehabilitation once mining ceases. Rehabilitation standards now include restoration of structural and functional attributes of pre-disturbed landscapes. However, insufficient baseline data before, and during, mining often makes it difficult to assess impacts and develop rehabilitation objectives. Techniques that retrospectively document the pre-impact condition and environmental history of wetlands affected by mines can provide this information. We demonstrate how this can be achieved using data from palaeoecology and remote sensing, to understand mine impact on Fishermans Wetland, North Stradbroke Island (Minjerribah), by inferring its environmental history from formation to present. Fishermans Wetland is a small, clear, open water, wetland with extensive macrophyte growth. A lack of information about the wetland's pre-mine condition created uncertainty about the effects of upstream sand mining. Contrary to local community concerns that Fishermans Wetland was ancient and hydrologically modified by mining, it only formed in the 1950s. Moreover, changes to site hydrology predated mining. Consequently, ongoing supplementation of water is unnecessary for maintaining the wetland's ecological character. Similar techniques could be used elsewhere where mine impacts are poorly understood or contested. [ABSTRACT FROM AUTHOR]

Polyunsaturated fatty acids (PUFA) are essential components of cell membranes and reproductive and sensory organs in vertebrates and are largely acquired through their diets. Accordingly, identification of the dietary sources of PUFA is an important consideration in food web studies.We collected fish, macroinvertebrates (aquatic and terrestrial), and plants (aquatic and terrestrial) from floodplain and river channel habitats in a tropical river catchment in northern Australia, to identify food sources and habitats that provided lipid and PUFA rich food that sustain fish populations.The composition of most FA in fish was similar to that reported from other freshwater tropical environments, with the exception of their higher arachidonic acid content. Fish were found to derive their fatty acids primarily from aquatic sources of food and had similar FA composition to aquatic macroinvertebrates. Aquatic macroinvertebrates fed on aquatic plants (algae) and had higher total lipids and FA contents than plants and fish, providing a more concentrated source of PUFA for fish. Fish obtained most of their FA from their diet except for docosahexaenoic acid (DHA), which they must synthesize due to low DHA in algae and macroinvertebrates.There was no overall difference in basal dietary FA composition between floodplain and river channel habitats. However, macroinvertebrate taxa varied in their lipid and PUFA content.Food quality for fish may therefore vary between habitats as a consequence of differences in macroinvertebrate community composition. Given the high algal production on floodplains compared to the river channels, these habitats are likely to represent the major source of high quality food for fish and other aquatic consumers, and conserving habitats that are rich in lipids and PUFA is important for maintaining healthy fish communities. [ABSTRACT FROM AUTHOR]