2019
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About the document
Between September 2018 and January 2019, 109.8 GL of water for the environment was delivered through Yanga National Park and Gayini Nimmie-Caira to Yanga Lake to protect the resident golden perch population by prevent Yanga Lake from drying-out and providing habitat for native fish, waterbirds, and other water-dependent animals.
Additional monitoring under the Long-Term Intervention Monitoring project was funded to address a range of environmental flows questions related to the importance of river-floodplain connections in supporting fish and waterbird populations.
Key findings of this monitoring included:
- Golden perch spawning and recruitment most likely occurred from within the floodplain system rather than movement from the river system as indicated by stable isotope analyses and catch data.
- Successful floodplain spawning and recruitment of golden perch was detected in Tala Creek and the hatch-dates of recruits over-lapped with environmental water delivery.
- The diet of common carp and recruit stages of golden perch overlapped, suggesting that the two species are in competition for food resources provided by floodplain inundation.
- Waterbird abundance increased a month after water for the environment connected to each of the lakes, Tala and Yanga.
- Piscivorous (fish eating) birds were the most abundant functional group of waterbirds at both Tala and Yanga Lakes in all survey months, with Australian pelicans being the most abundant.
- Waterbird abundance was the second highest since 2010 based on annual spring counts conducted by NSW Department of Planning, Industry and Environment.
The monitoring results suggest that water for the environment delivered to floodplain habitats during spring and summer are important for maintaining viable native fish populations and provide habitat for populations fish-eating waterbirds.
The golden perch recruitment event in 2018/19 was not widespread, but its potential importance to local populations should not be underestimated in a year following fish-kills and drought. During the extreme drought conditions and the fish-kills experienced in the Murrumbidgee in early 2019 and in other areas of the Murray-Darling Basin, these inundated floodplain habitats and lakes have provided refuges and productivity which support a diverse assemblage of waterbirds and contribute to fish spawning, growth and recruitment.