There is a need for reference data on by-catch by the commercial and recreational fisheries that operate in the Coorong Lagoons. These data will be used to identify management issues, prioritise management actions, and enable targets/solutions to be established in accordance with principles of Ecological Sustainable Development. The project is especially relevant to the LCF, which is a small-scale community fishery seeking accreditation with the Marine Stewardship Council sponsored by the World Wildlife Fund.
The need to investigate mechanisms for reducing recreational by-catch in the Lakes and Coorong fishery is emphasized by the high percentage (71%) of mulloway that are caught in this fishery and released (National Recreational and Indigenous Fishing Survey 2000/01).
The information gained from this project will guide management decisions about fisheries resources, and address industry, conservation and public concern about the impact of commercial and recreational fishing on the ecological sustainability of the LCF.
This project addresses several targeted priorities stated in Program 1 of the SAFRAB 5-Year R&D Strategy, aimed at ensuring sustainability of natural resources. Outputs from this project will inform stock assessment and management of the resource and contribute to sustainability. Outputs from this project will also contribute to development of environmental best-practice and complements a qualitative review of by-catch mitgation procedures undertaken by SAFIC and SeaNet (Anon. 2002).
This project also addresses key strategies identified in Goal 3 of the Draft Management Plan for the South Australian Lakes and Coorong Fishery (Sloan 2005). This concerns minimising fishery impacts on by-catch species by (i) quantification of the impact of fishing operations on by-catch species, (ii) improved recording of data on by-catch interactions and by-catch species composition and (iii) risk analysis to assess the vulnerability of by-catch species. Additionally, there is a need for baseline data on by-catch to set the levels for reference points and triggers outlined in the management plan.
There is also a need for a preliminary assessment of the survival of discards of key species from key recreational and commercial gear in the Coorong lagoons as emphasised by an independent reviewer.
Other projects where the need for quantitative data was justified by demonstrating that changes in gear and/or practices reduced by-catch or minimised mortality of discards were:
1. In N.S.W. estuarine fisheries, incorporation of strategically placed transparent netting in the bunts of haul nets significantly reduces the retention of unwanted by-catch (Gray & Kennelly, 2001).
2. In Victorian estuarine fisheries, changes in tow speed, tow duration, operating depths, sorting strategy, and mesh material have all been shown to improve the survival of released fish (Knuckey et al., 2002).
Although the results of any by-catch study is specific to the component species, fishing gears and practices, and the location of the fishery, the proposed project will, nevertheless, benefit from these completed projects by the general directions taken to develop new and innovative ideas to reduce by-catch.
This project will also address the needs of the ‘National Strategy for Conservation of Australia’s Biological Biodiversity’ of: (a) improving the knowledge base of commercial and recreational fisheries; (b) improving fisheries management in recreational and commercial sectors; and (c) assessing and minimising the impact of commercial fishery practices on non-target and by-catch species, ecosystem and genetic diversity.
Anon. (2002). Lakes and Coorong Fishery: Best practices to minimise interaction of juvenile mulloway, crabs and birds with fishing gear. Adelaide, Southern Fishermen’s Association, SEANET: 1-9.
Gray, C. A. & Kennelly, S. J. (2001). Development of discard-reducing gears and practices in the estuarine prawn and fish haul fisheries of NSW. FRDC Project No. 97/207.
Knuckey, I. A., Morison, A. K. & Ryan, D. K. (2002). The effects of haul seining in Victorian bays and inlets. FRDC Project No. 97/210.
Sloan (2005) Draft Management Plan for the South Australian Lakes and Coorong Fishery, The South Australian Fisheries Management Series, PIRSA (Fisheries Policy), Adelaide.
Final report
This project was developed by SARDI, in consultation with PIRSA, Lakes and Coorong Fishery (LCF) licence holders and relevant stakeholders, over several years. Proposals to investigate interactions with non-target species and discarding from the LCF in the Murray River estuary and Coorong lagoons were submitted to South Australian Fisheries Advisory Board (SA FRAB) and FRDC in 2002 and SA FRAB in 2003 but failed to gain industry support. In 2004 the Southern Fishermen’s Association expressed support for a study of non-target species to support their application for accreditation with the Marine Stewardship Council.
During the study the lower Murray River system was in drought, and high salinities and generally poor environmental conditions occurred in the Coorong lagoons. Consequently, the approaches to addressing objectives three and four (below) were changed. It was originally intended to estimate discard survival (Objective 3) from discards that had been held in sea cages over 5 days. Instead, discard survival was estimated from numbers of fish that were alive at net retrieval. The original approach to identify methods for mitigating levels of discarding (Objective 4) was to conduct experimental fishing. This objective was met using information available from the observer based monitoring program, from the peer reviewed literature and from several previous FRDC funded projects.
The main outcome of the project is the provision of information on catch species composition, quantified levels of discarding, and ongoing collection of data from the Lakes and Coorong Fishery. This was achieved using an observer based study of catches in the Lakes and Coorong Fishery. During 2005-06 a total of 53 observer trips were made (973 net shots), with 18 days (173 net shots) surveyed in the Murray River estuary and 35 fishing days (800 net shots) in the Coorong lagoons.
Keywords: gillnet, bycatch, discard, estuarine fish, observer program, Australia
