Threatened species benefit from environmental water
Endangered fish species such as the protected Australian grayling will benefit from a large release of environmental water into the Yarra River over coming weeks.
Commencing Thursday May 18, millions of litres of water will be released over a three week period from Upper Yarra and Maroondah Reservoirs. River levels can be expected to rise up to 90 cm in the Yarra and up to 120cm in Watts River during the release and are within the normal natural variation of these rivers.
The primary purpose of the release is to support juvenile Australian grayling migration and spawning.
Cheryl Edwards, Environmental Water Resources, Melbourne Water said the release was important for the success of the species.
“Australian grayling spawn in the freshwater reaches of the system before the eggs and larvae drift out to sea. Both the juveniles and parents spend approximately six months in the sea before they then migrate back upstream,” she said.
“Since the completion of the Dights Falls fishway (Abbotsford) in December 2012 the grayling have been successfully migrating further upstream.”
This environmental water release will increase their chances of breeding and provide the natural cue for the fish to migrate (on the back of the extra flow) downstream to spawn.
“Monitoring of the same event during recent years has shown evidence of grayling spawning. This, together with continued migration of juveniles over the Dights Falls fishway, indicates that the population of grayling in the Yarra is increasing.”
Australian grayling are not the only species to benefit. Macquarie perch spawn in riffle habitats (places where a river flows quickly over a pebble bed) and these locations tend to get clogged with silt during the year.
“The flow from environmental water releases enables the spawning grounds to be cleaned up in preparation for spawning and a steady stream flow allows the eggs to remain stable in the spawning grounds,” said Ms Edwards.
The first round of monitoring in late 2013 indicated that the Macquarie perch had a large spawning event after a water release and Melbourne Water will be sampling for this species again in 2017.
Other species expected to benefit from increased environmental flows include regionally significant River blackfish and the Platypus.
Melbourne Water will monitor the response of the river and aquatic life closely following the event to inform future environmental water releases. Melbourne Water works closely with the Victorian Environmental Water Holder and other stakeholders on all environmental water releases.
Technical details of the Yarra environmental water release:
- Commences Thursday 18 May from the Upper Yarra Reservoir and ceases release from the reservoirs on 15 June
- Release up to 12,000 million litres of water over a three week period
- Peak flows up to 600 ML/d for seven days at Millgrove ( 27 May – 4 June)
- Peak flows up to 1300 ML/d for seven days at Warrandyte ( 1 June – 7 June )
- Flow conditions will be monitored throughout the release and can be amended as required including ceasing the release if high rainfall occurs.
Joseph Keller, Senior Media Advisor. Ph. 0430 219 287 | 03 9654 3234