The Status of Murray Cod in the Murray-Darling Basin
Robert E. Kearney and Melissa A. Kildea
Applied Ecology Research Group, University of Canberra
Environment Australia, May 2001
About the publication
The Murray cod is Australia's icon freshwater fish. It is legendary and the mere mention of its name provokes public interest. It has been of unequalled significance to traditional, recreational and commercial fishers and unfortunately, the target for much illegal poaching.
Not only is it the biggest and most highly prized fish in the Murray-Darling Basin but it represents the best indicator species for the ecological status of the Basin as a whole. Its complex life history and the differing requirements of eggs, larvae, juveniles and adults necessitate integration of habitat availability and condition, water quantity and quality and impacts of directed targeting. Managing for Murray cod will equate to managing for ecosystem integrity.
Cod populations have declined dramatically since European settlement to the extent that cod are no longer common in many parts of the Basin. These declines can be attributed to several categories of anthropogenic influence, including habitat degradation, pollution, reduced environmental flows, barriers to migration and fishing.
Persistence of the species (species biodiversity) does not appear to be of immediate concern, but the integrity of wild populations (genetic biodiversity) and of the ecosystems which support them (ecological biodiversity) are seriously threatened.
The benefits of Basin-wide management, or at least complementarity of regional management, are emphasised.
Key knowledge requirements include:
- Better definition of the cultural significance and heritage value of Murray cod, particularly in relation to indigenous people and smaller riparian communities.
- Better indicators of spawning and recruitment success across the Basin.
- More detailed assessment of the hydrological factors which trigger spawning and support successful recruitment.
- Better understanding of the relationships between successful recruitment for cod and for other native species.
- Understanding why some cod populations have failed to recover even though causes of declines appear to have been corrected.
- Better evaluation, assessment and monitoring of genetic integrity of individual cod stocks.
- Assessment of the impact on wild cod populations, and broader aquatic ecosystems, of stocking of cod fingerlings.
- Quantification of the extent of illegal poaching of cod and identification of management strategies, including increased community education, to overcome the problem.
- Evaluation (quantification) of benefits and costs of recreational fisheries to local communities and to cod conservation throughout the Basin.
Suggested policy and management initiatives are:
- There needs to be clearly stated objectives for the management and use of all native fish within the Basin.
- Resource conservation principles and management triggers related to resource sustainability should be given priority over resource allocation issues.
- Management of targeted use, including allocation of Murray cod resources, should be aligned with the assessed impacts of each type of targeting and the costs and benefits of each harvest strategy.
- More effective management (elimination) of illegal traps and nets is required.
- Clearly stated policies and management objectives for recreational fisheries, which promote resource conservation and more equitable sharing of allocations within the recreational sector are required.
- The stocking of hatchery produced fingerlings, particularly into rivers and flood-prone impoundments, requires regulation. Clear objectives, procedures for assessment of anticipated impacts and monitoring protocols are required urgently.