This study is seen as a platform that will pave the way for a committed ongoing program of assessing, refining and ultimately adopting bycatch mitigation strategies in temperate South Australian prawn fisheries. This project was conceived from a high priority need to develop and test enhanced gear technologies that aim to: 1) reduce the incidental capture of bycatch species and 2) reduce the capture of small prawns. Both have the potential to maximise the value of the resource. This need was highlighted in the recent Gulf St Vincent prawn fishery (GSVPF) assessment report (Roberts et al., 2009).

The GSVPF is about to embark on a bycatch risk assessment process that will include a bycatch survey (March 2010), which will provide a unique opportunity to conduct this research in parallel at a significantly reduced cost.

This project will provide a template that utilises current fishery-independent trawl surveys to test new gear technologies. This work would follow on from previous valuable catch selectivity research (square mesh), and will provide management and industry with options for the way forward in terms of bycatch mitigation. This project will evaluate the effectiveness of novel trawl mesh (T90) at optimising catch selectivity and will be underpinned by pilot trials to be conducted at the expense of industry and SARDI. Furthermore, valuable underwater footage of operational trawl nets will be captured for the purpose of informing and optimising current and future net modifications / BRD trials (gear and bycatch behaviour). Information on species-specific trawl vulnerability, behaviour and differences in gear designs would augment the ecological risk assessment that the industry are undergoing.

Gear modifications trialled in Project 2008/017 included: (1) a rigid-frame, steel mesh cod end and (2) a collapsible, nylon mesh cod end. These reduced bycatch of platypuses in fyke nets, and increased the likelihood of survival of other non-target species, without impacting the commercial eel catch.

However, the project identified some limitations with the gear modifications:

1. Clearing the catch from the rigid-framed nets was considerably easier than from the collapsible nets. However, the bulky construction of the rigid-framed nets restricted the numbers which could be safely transported on board a commercial 4m eel punt to a maximum of 2-3 nets. Feedback from industry has identified that operators would need to be able to transport and work at least 5-10 modified nets at once to justify the use of such nets from a commercial perspective.

2. The nylon mesh nets were more flexible and could be folded and stacked flat on the floor of a boat, allowing a larger number to be carried at once. However, the main disadvantage with this design is the difficulty in clearing the catch, as these nets are cumbersome to handle.

Industry has recognised that the gear modifications improved bycatch management in the fishery. However, the Victorian Eel Fishermen's Association has highlighted that the weaknesses described above are major impediments to the adoption by industry of the modified gear.

A key recommendation of project 2008/017 therefore was the further refinement of gear modifications to maximise the likelihood of uptake of the modified gear by industry. The Project Investigators and the Victorian Eel Fishermen's Association have identified a number of opportunities for the further development of the gear to improve its efficiency, and therefore increase the likelihood of uptake by industry. Such developments need to be made for industry to take full advantage of the project findings.