Environmental water for fish and a special plant called ‘ruppia’ in 2017-2018

Environmental water for fish and a special plant called ‘ruppia’ in 2017-2018

We caught up with Carl Binning from the MDBA to find out about the priorities for environmental water in 2017-18.

To make the best use of water available for the environment, each year the Murray-Darling Basin Authority (MDBA) identifies which rivers, wetlands and floodplains are the priority for watering across the basin. We work with environmental water holders and managers to develop these priorities.

High flows in 2016 were good news for many parts of the Basin, but many sites and species need follow-up watering to build on these benefits, and boost their resilience for the dry periods ahead.

Along with our partners we have identified priorities for native fish, waterbirds, native vegetation and river flows in 2017-18.

Flows for Fish

We have already seen great results from last year, which we are now building on. For example, in spring and summer 2016, environmental water delivered to the Lower Darling helped maintain habitat and food for Murray Cod, and led to a large breeding event in the Lower Darling.

Meanwhile, in the north, good rainfall resulted in flows ideal for Golden Perch spawning leading to eggs and juveniles being washed into the Menindee Lakes. Food in the lakes helped these fish to thrive. Environmental flows were then used to release the Golden Perch from the lakes into the Lower Darling and the Darling Anabranch.

This year, the environmental watering priorities aim to encourage these one-year-old Golden Perch to spread even further through the system. The right flows will cue young fish to move upstream, downstream, and into tributaries of the Murray, where they will increase the number of fish found in rivers like the Goulburn, Campaspe and Edward Wakool.

Fish also did well in the mid-Murray River. Silver Perch are a threatened species, they breed regularly in the mid-Murray River (Torrumbarry to Euston), but their survival is much higher following years when flooding has occurred. As a result of flooding in 2016, there are currently good numbers of one-to-two year-old Silver Perch in the mid-Murray River. These young fish are highly mobile and need to move to habitat that is better suited for growing into adults. Without regular recruitment of young fish to adulthood, this species continues to be under serious risk.

One of this year’s priorities aims to provide flows that trigger these young Silver Perch to migrate upstream and into tributaries like the Goulburn, Loddon and Campaspe Rivers. Flows need to be coordinated and timed correctly so that the fish receive the right signals to migrate and find the right habitat. These signals have been lost under traditional river operations so we are not reinstating them using environmental water. Silver Perch that colonise the tributaries until they reach breeding age, can then contribute to future breeding events in the Murray, and provide a more resilient population.

Ruppia results

We have also seen some good results in places like the Coorong at the mouth of the Murray River. In 2016, we had continuous flows through the barrages and low salinity levels in the South Lagoon of the Coorong. Environmental water that had been used for other watering actions upstream contributed to these flows and the reduction in salinity.

Ruppia tuberosa is a plant that grows in the South Lagoon of the Coorong and provides food resources for waterbirds and habitat for native fish and macroinvertebrates. It is a key indicator of the health of the Coorong and the flows supported a germination event of Ruppia tuberosa. Unfortunately, even though we had good conditions for Ruppia to grow and set seed, algae started growing over the plants and their flower-heads, which destroyed them before they could produce seeds. So while we had good conditions and Ruppia flowered, it wasn’t able to produce a viable seed set to build its resilience for next year.

Ruppia tuberosa

The Ruppia experience is an example of why it is going to take some time to improve the health of the Basin’s environment. Sometimes things happen that we don’t anticipate as we are still building our knowledge of these complex ecosystems and it is going to take the right climate conditions, water planning, coordination and delivery over multiple years to make a difference.

Another priority for this year is to work on our long-term goal of improving the connectivity between freshwater, estuarine and marine environments in the Coorong, Lower lakes and Murray Mouth to boost habitat condition and support the ecosystems that depend upon flows for their survival.

The 2017-18 annual watering priorities are available on the MDBA’s website.

This article was written by Carl Binning.

You can download a pdf of the article ‘Watering in 2017-18’.
More information is available at https://www.mdba.gov.au/publications/mdba-reports/basin-annual-environmental-watering-priorities-2017-18.
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Sophie Van Dijk

Sophie Van Dijk

Sophie works with Finterest and the Australian River Restoration Centre team to ensure that there are always new and interesting fishy stories for you to enjoy, both on the website and on social media.
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