Last week was the annual release of more than 5000 Murray cod fingerlings into the Macquarie River from the Narromine boat ramp thanks to the partnership and donation of the Narromine Shire Council and Macquarie Cotton Growers. Murray Cod is the largest freshwater fish in Australia and is an iconic species with cultural and historical significance.
An innovative project to study Murray Cod is now underway, thanks to $50,000 in funding from the NSW Recreational Freshwater Fishing Trust, Industry and Investment NSW. Principal Research Scientist at the Grafton Institute Dr Stuart Rowland said, “Murray Cod, the largest freshwater fish in Australia, is a premier recreational fish that is now listed as a vulnerable species by the Commonwealth Government.
“A number of factors have contributed to the decline of Murray Cod, including over exploitation by commercial and recreational fisheries, predation by introduced fish, and habitat degradation.
“This research project will determine key aspects of Murray Cod reproduction in selected parts of the northern Murray-Darling River System. The project will complement various management programs based on research findings that have already been undertaken during the past two decades to promote a recovery of Murray Cod.”
“Murray Cod is the key native freshwater recreational species in NSW, and any information that can contribute to improved management will ultimately enhance stocks of Murray Cod and directly benefit recreational anglers.
“Most of the previous research on Murray Cod has been done in southern tributaries of the Murray-Darling System, and there are potentially significant differences between cod populations in southern and northern areas,” Dr Rowland said.
Consequently it is important to study cod in the northern tributaries to ensure efficient management across the entire system.
“Our project will provide information on the movement of adult fish, the type and location of spawning sites, spawning behaviour, parental protection of eggs and larvae, effects of coldwater pollution, and the timing and duration of the breeding season in the northern tributaries.
“In addition, the project may provide information on an important, much debated and at times emotive aspect of Murray Cod reproductive biology: do very large Murray Cod (e.g. greater than 100cm) breed and contribute to the reproductive output of the species.
“There is some evidence that large cod may not be active and/or successful breeders,” Dr Rowland said.
The funding will be used to select rivers and study sites in different habitat types (upland and lowland), purchase tags and equipment, and enable collaboration with recreational fishers and fishing groups, scientists and managers, and staff of other fisheries agencies.
Narromine has been doing its part in preserving and boosting the numbers of Murray Cod in the river system since 1994, and with the annual release of the fingerlings into the Macquarie River from the shire and other towns such as Warren, this should help decrease the vulnerability of the species.
“Intensive fish surveys will be done at each site using a boat-mounted electrofishing unit to determine species present, and the size frequency and age structure of Murray Cod,” Dr Rowland said.
“Radio tags will be surgically implanted in individual cod and used to monitor their movements and behaviour at each site. Some large cod, greater than 100 cm will be tagged in an attempt to determine their reproductive contribution. In addition, underwater cameras will be strategically located to observe fish and their breeding behaviour.”
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