Monitoring Murray cod spawning & recruitment in response to spring 2020 Macquarie River environmental water flows

About the document

In 2020–21, Commonwealth and NSW environmental water managers delivered water for the environment to support the recovery of native fish in the mid-Macquarie River, and core wetland vegetation in the Macquarie Marshes.

The Commonwealth Environmental Water Office contracted the NSW Department of Primary Industries – Fisheries to monitor the spawning and recruitment response of Murray cod to this delivery of water.

For many decades, native fish populations in the Macquarie River have been impacted by water resource development, loss of habitat and the presence of barriers. Native fish also suffered from extreme drought conditions between 2017 and early 2020.

As refuges began to dry, passionate locals and NSW Department of Primary Industries–Fisheries rescued and relocated hundreds of native fish including Murray cod to safer waterholes in the Macquarie River. When rain begin to fall again there were several fish death events in the Macquarie catchment.

The ongoing delivery of water from the environment in the Macquarie River, and the learnings from this monitoring, will help these native fish populations to recover.

Key findings from the project included:

• Successful spawning and juvenile recruitment of Murray cod was observed during the 2020–21 watering year within the mid-Macquarie River. This can likely be attributed to deliveries of water for the environment in spring.
• The larvae of five fish species were found during the delivery of water for the environment in October including Murray cod, Freshwater Catfish, Common Carp, Golden Perch and Australian Smelt. Murray cod made up 88% of the larvae caught.
• Early life stages of yabbies and freshwater mussels and drifting eggs of silver perch were also observed.
• Without deliveries of water for the environment, flows in the Mid-Macquarie River around Dubbo and Narromine would have fallen below the target thresholds throughout most of September and October 2020. This would have reduced the available nesting habitat for Murray cod and freshwater catfish causing potential nest abandonment and nest drying.

This monitoring project provides valuable information of the breeding and recruitment of Murray cod in the Macquarie River, which will help inform the future delivery of water for the environment in the Macquarie catchment to support native fish such as Murray cod.