Budget expenditure: $355,509.00
Project Status:
Current
Principal Investigator: Ryan Day
Organisation: University of Tasmania (UTAS)
Project start/end date: 31 Dec 2021 - 30 Dec 2023
Contact:
FRDC
SPECIES
Commercial Scallop

Need

Commercial scallop is fished by dredging in 3 jurisdictions, with Tasmania (TSF) and Victoria currently classified as depleted. The 3rd jurisdiction, the BSCZSF, closes some scallop beds to fishing while the rest of the fishery remains open for harvesting. The closed beds and the 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. The TSF only opens a small area of the fishery following annual dredge surveys, with the remainder closed. However, the issue of the estimation of recruitment and sensitivity of juveniles to dredging during surveys and fishing is still relevant, as only those beds with > 80% legal sized scallops are opened. 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. AFMA and Tasmanian DPIPWE resource managers and industry members are committed to further investigating and optimising 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, which will in turn inform management decisions, such as area closures and setting of TACs, and contribute to more sustainable fisheries.

Objectives

1. Undertake a Commercial Scallop Fisheries review and a targeted desktop study examining current approaches used for video survey of scallop stocks
2. Determine the best video survey approaches for the scale of the Commercial Scallop Fisheries and build and test multiple prototype video survey platforms
3. Undertake scallop video surveys in shallow inshore waters using the prototype video survey platforms and ground truth with diver and dredge surveys
4. Undertake data analysis trials, with the aim of developing partial machine learning solutions for data analysis
5. Apply learnings from inshore surveys and undertake an offshore video survey using the final video survey platform design and ground truth with a dredge survey
6. Synthesise results, compare dredge and video survey methods, propose an optimal design of a video survey platform and data analysis regime for commercial scallops in both inshore and offshore waters, and develop pathways to adoption

Related research

Environment
Adoption
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