Golden opportunity to trigger native fish spawning

Thursday 5 November, 2020
For the first time in four years conditions are ripe for large-scale golden perch migration and spawning in the Goulburn River.

The keys to successful golden perch spawning are warmer water temperatures (between 18C and 22C) and higher flows of around 7000 megalitres a day in late spring. Due to river regulation and recent years’ dry weather, these conditions have not been met for several years and monitoring indicates there has been limited golden perch spawning and recruitment throughout the Murray Darling Basin.  Lack of young fish in the river system may lead to future declines in population abundance and sustainability.

“Recently, however, monitoring picked up golden perch larvae in the lower Goulburn River,” Goulburn Broken CMA’s Simon Casanelia said.

“This is terrific news. With nutrient-rich run-off and inflows from tributaries after recent rain providing plenty of fish food, good flows in the Goulburn and Murray rivers allowing fish to move up and downstream, and water temperatures hovering just above 18C the signs are all pointing to a good native fish spawning event. And, for the first time in a while we’re in a position to give nature a helping hand by using water for the environment in late spring to maintain higher flows in the Goulburn.

Water for the environment is due to be released from Goulburn Weir from November 12. It will peak around 7100 megalitres a day (river height 3.73 metres) at Murchison on November 17 before slowly receding to current levels (about 830 megalitres a day, river height 0.72 metres) by November 26. If there is heavy rain during that time the flow may be reduced or not go ahead. The lower Goulburn River environmental flow will be over by cod opening (December 1).

Similar river and weather conditions occurred in 2016 and led to large-scale golden perch movement and spawning.

Monitoring of golden perch movement and spawning is under way and will continue until December. Monitoring is also carried out in autumn each year to assess changes in native fish numbers. The monitoring is undertaken by Arthur Rylah Institute staff as part of the Commonwealth Environmental Water Office’s Monitoring Evaluation and Research (Flow-MER) project. The results are used to measure ecological responses to environmental water management.

The use of water for the environment during spring increases flows at the time of year that is beneficial to the environment. Due to community concerns about high flows in summer and autumn in recent years, the Victorian Government has announced an interim operating rule for 2020/21 aiming to limit inter-valley trade water (water traded between the Goulburn and the Murray) to 40 gigalitres a month during summer and early autumn to protect the lower Goulburn River environment.

Environmental flows are planned by the Goulburn Broken CMA in consultation with the Commonwealth Environmental Water Office and the Victorian Environmental Water Holder. The delivery is managed by Goulburn-Murray Water in line with the VEWH’s Seasonal Watering Plan 2020-21.Timing of the environmental flows takes into consideration delivery orders by irrigators and other water users and feedback from the community via the Goulburn Broken CMA’s environmental water advisory groups.

Providing water for the environment is only one way of protecting and improving rivers and wetlands. Fencing and revegetation, erosion control, pest control, returning logs to rivers (re-snagging) for fish and bug habitat, and installation of fishways to allow fish to pass through dams and weirs also help. Find out more about river health, water for the environment and monitoring activities at www.gbcma.vic.gov.au

To check flows in the Lower Goulburn, view the hydrograph on Goulburn Broken CMA’s website:  http://fchmccoys.hydronet.com/ (updated weekly).