There are three commercial Prawn fisheries in South Australia: Spencer Gulf Prawn Fishery (SGPF); Gulf St Vincent Prawn Fishery (GSVPF); and West Coast Prawn Fishery (WCPF). All exclusively target the Western King Prawn (Penaeus (Melicertus) latisulcatus). The SGPF is the largest in terms of total area (22,367 km2), production (latest 10-year mean: 1,853 t p.a.), and number of licence holders / vessels (39). The WCPF is the smallest of the prawn fisheries with three licences (68 t in 2021). There are currently 10 commercial fishing licences issued for the GSVPF with production in 2021/22 at 138.5 t. Balmain Bugs (Ibacus spp.) and Southern Calamari (Sepioteuthis australis) may be retained as byproduct in each fishery.
There is ongoing interest in maintaining a program that assesses, refines and ultimately adopts bycatch mitigation strategies. Steps taken to reduce bycatch and / or discard mortalities in South Australia include avoidance (i.e. spatial and temporal closures and reduced trawl footprint), changes to on-board handling (i.e. ‘crab bag’, sorting grid, hopper with water flow-through system), and trialling and / or use of bycatch reduction devices (i.e. Nordmøre grid, Tom's fisheye, T90 cod-end / grid design modifications) and tools (i.e. LEDs). However, the benefits of some of these bycatch mitigation strategies are not fully understood (e.g. LEDs, Tom’s fisheye) and further development is needed to achieve optimum outcomes for the resource, industry, and the environment. There is a genuine interest from industry to assess catch efficiency and selectivity of different trawl systems (e.g. quad versus double rig) and net configurations (e.g changes to cod-end and trawl body) in GSVPF and LED configurations / colours in SGPF to determine impacts on prawn catch and bycatch.
Our study aims to 1) Assess the effectiveness of LEDs in reducing bycatch, while minimizing prawn loss, in the SGPF; 2) Test the effects of trawl systems (e.g. quad vs double rig) and net configurations (e.g. changes to cod-end and trawl body) on trawl efficiency and catch selectivity in the GSVPF; and 3) Build on existing cost-benefit analysis knowledge and tools (i.e. FRDC 2011-209 , FRDC 2011-750 and FRDC 2016-213) to quantify the economic / productivity outcomes of prawn trawl modifications.
This project directly addresses South Australian Prawn Fishery’s research needs (i.e. research plans proposed by the GSVPFMAC and SGPF RSC) and will showcase the potential for further bycatch mitigation to increase fishing yield, value, and profitability while reducing bycatch. Furthermore, the outputs can be extended through the Australian Council of Prawn Fisheries (ACPF) to other Australian prawn trawl fisheries that have similar needs to mitigate and monitor bycatch.
