Bycatch in fisheries is the number one source of direct human-caused death and serious injury to marine mammals worldwide. Many Australian fisheries have interactions with marine mammals, which they are required to minimise and mitigate under the Environment Protection and Biodiversity Conservation Act (EPBC,1999) and other relevant State legislations. In addition, new US Government legislation requires nations importing seafood into the US to demonstrate that they have a regulatory program for reducing marine mammal bycatch that are comparable in effectiveness to the US standards. Operational interactions between the South Australian Sardine Fishery (SASF) and short-beaked common dolphins (Delphinus delphis) primarily occur when individuals become encircled in the purse seine net after it has been set. The application of an industry code of practice in the SASF has resulted in a marked reduction in dolphin interactions but the impact of bycatch on common dolphin population has not be assessed. This investment will estimate the abundance of common dolphins in core fishing areas of the SASF and develop population models to evaluate bycatch limits of common dolphins and assess the sustainability of interactions with the SASF.