2019
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About the document
In spring and summer 2017-18, the Commonwealth Environmental Water Office, Murray-Darling Basin Authority and South Australian Department for Environment and Water jointly commissioned the South Australian Research and Development Institute (SARDI) to undertake monitoring to assess the salt wedge conditions and black bream (Acanthopagrus butcheri) recruitment associated with Murray barrage releases, and to evaluate the contribution of environmental water to the ecological outcomes.
The monitoring during the spring/summer environmental water releases suggested that suitable larval nursery habitat was present in the Coorong. Conditions including salinities, stratification (fresher water overlying saltier water), temperature and dissolved oxygen were all found to be favourable to support black bream recruitment. In autumn 2018, young-of-year black bream were detected throughout the Murray estuary and North Lagoon in the highest abundances seen in the last nine years of monitoring. Spawn dates of the young-of-year bream suggested that spawning occurred slightly later than expected, from late December to early February, commencing about 1-2 weeks after the peak of the flow pulse.
This study demonstrated that Murray barrages can be managed to deliver environmental water in a way that generates suitable conditions (particularly salt wedge habitat) to facilitate successful black bream recruitment events, which over time should support recovery of the Coorong black bream population. Without environmental water, the favourable conditions that supported the 2017-18 black bream recruitment would not have been present. This information will support adaptive management of environmental water and contribute to optimising barrage flow regimes to improve estuarine habitat and enhance recruitment of black bream and other estuarine fishes in the Coorong.
SA Department for Environment and Water has released two news articles about the black bream recruitment event:
- Baby black bream fish return to the Coorong - 2 May 2018
- New generation of black bream appearing in the Coorong - 30 April 2019