Murray cod (Maccullochella peelii peelii) aquaculture is a new and developing industry in inland Australia which features efficient and profitable use of natural resources (water and fish) in regional Victoria, NSW and Queensland. Farmed Murray cod is a premium product in domestic markets and small quantities are being sold in markets overseas. In north western Victoria the industry is centred around existing horticulture enterprises and aims to add value to large water holdings by applying multiple use to this precious resource. Culture of Murray cod in agricultural dams has enormous potential.

Pathogens affecting Murray cod and silver perch have been previously documented (see attached). However the incidence of disease outbreaks relative to major events in the fish life cycle and horticultural water supply practices in integrated farming systems has not been addressed. Farmers without easy access to pathology services and veterinary professionals need to develop skills in basic gross pathology and interpretation of wet preparations. This project aims to equip isolated farmers with these skills and also to document temporally when major disease outbreaks are likely to occur, what the most likely cause is and how the effect of these events can be mitigated.

Further development of fish culture in horticultural enterprises requires some capacity to advise prospective farmers of the capital costs, suitability of their water holding and other features that would affect potential profitability. Combined with data from other work it is planned that a model will be developed that can guide farmer decision making on the feasibility of embarking upon aquaculture within their horticultural enterprise.

This project relates to R&D plans 7.2.2, 7.2.4, 7.2.5 and 7.2.6. There are elements of disease control and mitigation, best practice plan development and training across the 3 parts of the proposal.

Better understanding of the impacts of stocking was flagged as a key national issue by the recent FRDC sponsored workshop on fish stocking. Stocked fisheries now represent an alternative recreational fishery that simultaneously reduces fishing pressure on marine fish stocks and delivers considerable social and economic benefits to regional communities. An aging population and increased leisure time for workers will create additional demands for fishing in the future. The continued success of freshwater fish stocking in Queensland and other States is contingent on demonstrating it is sustainable under the principles of ESD. The impacts of fish stocking on recipient ecosystems and wild fish stocks are poorly understood and these activities have drawn adverse criticism from conservation groups and environmental management agencies.

On a national scale, the Department of the Environment and Water Resources are driving sustainability issues via the EPBC Act with stocking fish outside their native range being nominated as a threatening process. Within Queensland all native fish stocking applications are assessed on their risk to local aquatic communities; other States have similar procedures. However, the decision making processes are poorly supported by data related to the likely ecological risks of the proposed stocking activities. These data cannot be obtained solely from desk-top studies that draw largely on overseas literature. What is urgently needed is pertinent research, done in an Australian context, to address key data deficiencies including impacts of stocking fish outside their natural range, displacement of natural populations and loss of genetic diversity. To do this effectively and to promote “world’s best practice” in our stocking industry, the issues first need to be succinctly defined and then appropriate methodologies developed to address them in research projects.

Murray cod is Australia’s highest profile freshwater fish species and there is a very high public expectation that fisheries for this species are managed sustainably.

There is general agreement that cod numbers have declined considerably since European settlement and whilst the exact reasons may be varied, it is clear that continued harvest is one identifiable factor that has the potential to hinder recovery. However, there is general uncertainty about a number of critical issues relating to the management of these fisheries.

A number of information gaps have been identified in relation to the recreational fisheries as follows;
- There is broad detail available on gross angler harvest but there is no detailed information on catch related to individual rivers or basins, or the level of indigenous use .
- The LML of 50cm is a critical issue as evidenced by the rapid decline in numbers of fish above this level. This also means that the survival of released fish is highly relevant.
- There is a lack of information on population structure and dynamics and, with particular reference to recreational fisheries management, there is uncertainty regarding size at maturity and whether this is constant across the basin.

Current regulations may allow the removal of fish that are sexually immature. At low fishing pressures, this may be tolerable, however, at high fishing pressure, removing spawners before they mature may threaten a stock. The management of Murray cod populations requires that the LML chosen must be robust to both fisheries management and conservation requirements, but there has been no assessment to determine the appropriate LML for sustaining these fisheries.

The information from the size at maturity as well as harvest levels and hooking survival estimates will enable the impacts of recreational fishing on cod populations to be determined via management scenario testing.