Management and mitigation of the bycatch of protected species is required under the EPBC Act and the Fisheries Act. Bycatch trigger limits provide a framework to manage marine mammal bycatch rates and are used by AFMA in the management of the SPF and in the gillnet sector of the Southern and Eastern Scalefish and Shark Fishery (SESSF). The setting of trigger limits requires quantitative information on population size to ensure that the impact of fishing mortality does not negatively affect population status.
Robust population estimates do not exist for most marine mammal species in Australian waters and are particularly limited for cetaceans and there is also limited to no information on the distribution and population structure of these species. Bycatch trigger limits need to consider the smallest population unit to ensure that levels of anthropogenic mortality are sustainable.
Where data are sparse, it can be difficult to reach consensus between different stakeholder groups on the validity of management measures, particularly in relation to trigger limits. By eliciting expert knowledge through a formally structured system, a transparent process of evaluating and synthesising current data and quantifying the uncertainty around proposed bycatch trigger limits is available for managers and can be used to build industry and stakeholder support. This is particularly important when considering the management of bycatch impacts on populations that interact with a number of different jurisdictions.