Body size mediated effects of multiple abiotic stressors on the growth and social behaviour of an estuarine fish, Australian Bass (Macquaria novemaculeata)

Anthropogenic climate change is expected to result in dramatic shifts in the abiotic conditions within estuaries, including an elevation of temperature and salinity levels. Even so, few studies have addressed the impacts of multiple abiotic stressors on the behaviour and life history of key estuarine species, such as those of biological and commercial importance. Here we used a cross-factored experimental design to tease apart the effects of temperature and salinity on intraspecific aggression and growth rates of a native estuarine fish species, the Australian bass (Macquaria novemaculeata). Juvenile bass were exposed to one of four treatment conditions: 1) baseline temperature and salinity, 2) elevated temperature, 3) elevated salinity, and 4) elevated temperature and salinity. Elevated salinity increased rates of aggression, and elevated temperature decreased rates of growth, although the effects of both factors were mediated by the body size of individual bass. These results therefore highlight complex and variable effects of abiotic stressors and body size, emphasising the importance of considering individual-level attributes when evaluating the impacts of climate change on estuarine fishes

Estuarine characteristics, water quality and heavy metal contamination as determinants of fish species composition in intermittently open estuaries

Estuaries are critical aquatic environments that are used by many fish during their life cycle. However, estuaries often suffer from poor water quality as a result of anthropogenic activities. Fish diversity studies in estuaries are common, although few have examined whether correlations exist between water quality, metal contamination and fish assemblages. In the present study we investigated the effect of abiotic conditions, heavy metals and estuary characteristics on the abundance, diversity and composition of fish in four intermittently open estuaries along the Illawarra coast of south-eastern Australia. The heterogeneity of environmental conditions was reflected in the fish assemblages in each estuary. Environmental variables predicted fish species composition, and estuaries in particularly poor condition contained few species (estuarine residents) in high abundance, indicating their ability to acclimatise and survive in conditions that are hostile to other species. Overall, these findings demonstrate that estuarine fish assemblages may be useful indicators of estuary condition and reveal the importance of managing anthropogenic activities in the surrounding catchment to improve water quality so that biodiversity of fish can be restored in these estuarine environments

Bioregional assessment project: Sydney Metropolitan, Southern Rivers and Hawkesbury-Nepean Catchments: data collation phase to study the impact of mining activity and coal seam gas on environmental assets

This study was commissioned by the Hawkesbury-Nepean (HNCMA), Sydney Metropolitan (SMCMA) and Southern Rivers (SRCMA) Catchment Management Authorities and undertaken by the University of Wollongong to collate existing data and to provide a preliminary assessment of the potential impacts of coal seam gas (CSG) and coal mining activities on environmental assets within the three CMA regions, where environmental assets were defined under three broad themes; water, land and biodiversity. This study formed part of the Australian Federal Government’s Department of Sustainability, Environment, Water, Population and Communities (SEWPaC) Bioregional Assessment initiative within regions potentially affected by CSG and coal mining activities. The key components of this study included: Creating a database (using on the SEWPaC supplied template) identifying key environmental assets (groundwater, surface water, wetlands, land use, soils, vegetation and threatened species) within each of the three CMA regions. Providing a list of the key GIS datasets used to compile the database and their sources. Providing this report which outlines findings in relation to potential impacts and hazards of coal seam gas and mining activity on these environmental assets. Identifying knowledge and data gaps, and providing recommendations for future research