Commercial scallop is fished by dredging in three jurisdictions, with Tasmania (TSF) and Victoria currently classified as depleted. The third jurisdiction, the Bass Strait Central Zone Scallop Fishery, closes some scallop beds to fishing while the rest of the fishery remains open for harvesting. The closed beds and the Total Allowable Catch (TAC) are informed by an annual dredge survey. These surveys also give an indication of recruitment within the fishery. However, the size selectivity of the dredges is not considered in this process, which may result in an under-estimation of recruitment. The need to minimise disturbance to juvenile beds to reduce mortality of small scallops through survey activities is also a consideration. Currently the only options for known juvenile scallop beds are to not survey them or to conduct a minimal number of dredge shots, noting that commercial dredges do not effectively sample juveniles.

Comparison of TSF 2020 video survey results with dredge survey results demonstrated much greater size selectivity by scallop dredges for legal-sized scallops than was previously thought, such that relying on dredge surveys alone to inform management decisions may be jeopardising the sustainability of the fishery. Along with the need to define the size distribution of scallop beds more accurately within the fishing zones, both Tasmania and the Commonwealth have areas closed to scallop fishing that contain an unknown scallop biomass that may contribute to recruitment.

This project aims to further investigate and optimise the use of towed video surveys to provide a survey method for both inshore and offshore waters to estimate both legal and sub-legal scallop density/biomass in fishery zones, as well as areas closed to dredging and known juvenile beds. This work will inform management decisions, such as area closures and setting of TACs, and contribute to more sustainable fisheries.