Healthy fish populations are a fundamental element of thriving coastal ecosystems and indeed an integral part of Australian life. There is an expectation that these ecosystems will be biodiverse and productive into the future, serving to underpin a huge variety of cultural, social, recreational and economic activities that depend upon them. Yet the ecosystem services that we derive from fish within estuaries are threatened by human pressures such as foreshore development which can dramatically alter or destroy the natural habitats – especially nursery habitats. Understanding the impacts of large-scale coastal developments on fishes is a critical knowledge gap and has been identified as a priority threat in the NSW Marine Estate Threat and Risk Assessment. Here, we will provide a quantitative assessment of the size and relative abundance patterns of fishes within the highly altered Gamay (Botany Bay) and relatively pristine Jervis Bay utilising stereo-BRUVs. These patterns will be interpreted to infer the potential effects of coastal modification on the fish assemblages and will provide an understanding of the ways the impacts of such development can be minimised. The project team has direct links with relevant management agencies to ensure the translation of outcomes and their extension to other temperate estuaries along the Australian coastline.