Flow optimisation has demonstrated benefits for fish and crayfish (#76)
Chris Bloink
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- Ecology Australia, Thomastown, VIC, Australia
- Limited environmental water entitlement during 2018-19 meant that recommended flows for the mid and lower MacKenzie River and upper Burnt Creek could not be met. Previously, this scenario resulted in ‘system resets’ where refuge pools were expected to have dried out (e.g. 2012/13 and 2014/15). Watering in 2016/17 and 2017/18 allowed re-establishment of important fish and crayfish populations.
- Ecology Australia worked with the Wimmera CMA to avoid another ‘system reset’. This included identification of key refuge pools, rapid collection of baseline fish and crayfish data, workshopping optimal autumn/summer watering regime, critical refuge pool depth thresholds and depth monitoring, followed by post implementation rapid survey to assess population persistence, and repeat surveys in subsequent years (2020, 2022) including post flood (2023).
- The delivery of periodic low flows to each system to conserve refuge pools as a top priority, followed by winter/spring releases conducive to spawning for obscure galaxias when sufficient water is available, was prioritized over the delivery of summer and autumn freshes previously included as high priority (tier 1a) flows under all planning scenarios. Self-sustaining populations of target species persisted at all refuge sites in 2019 and subsequent monitoring years. Potential exists for re-introduction of river blackfish, a species lost from Burnt Creek during the Millenium Drought.
- Environmental entitlement volumes fluctuate over time and the full range of watering actions recommended by FLOWS studies are often unable to be delivered. It is critical that when water availability is limited, refuges must be maintained for aquatic values to persist.
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