Public scrutiny of trawl impacts on seafloor ecosystems is ever increasing, and demonstrating the sustainability of trawling on different areas of the seafloor is challenging. Well-managed trawl fisheries employ best practices to achieve sustainable levels of fish production while minimising their ecological impact. The Spencer Gulf Prawn Fishery operates in the Spencer Gulf of South Australia and has held Marine Stewardship Council certification since 2011. We characterised seafloor habitats and selected trawl by-catch species in Spencer Gulf, and quantified and assessed the risks and impacts of prawn trawling. Underwater towed video transects were used to collect new data on seafloor habitats, which were combined with historical datasets of biological and environmental variables and trawl effort to model, predict and map the distribution of habitat types and trawl intensity across Spencer Gulf. The exposure to trawl-effort intensity (number of times trawled per year) was calculated for the predicted distributions of 11 biological seafloor habitats and 58 by-catch species. Regional average seafloor status relative to an untrawled state (equal to 1) was high (>0.90) and was estimated using a risk assessment model that included depletion and recovery parameters for taxonomic groups.