Lower Darling Baaka River freshwater mussel pilot study

Nicole McCasker, Iain Ellis, Karen Danaher, Paula D'Santos

Research output: Book/ReportCommissioned report (public)

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Since 2000, the lower Darling Baaka River (LDBR) has experienced an increase in droughts and cease-to-flow conditions. Exacerbated by reduced inflows from the northern Murray-Darling Basin, cease-to-flow events during the most recent two droughts, 2015-16 and 2018-2020, lasted 17 and 18 months, respectively, the longest since records began in 1885. These ceaseto-flow events left large parts of the LDBR dry, leaving only isolated refuge pools, which in turn experienced water quality declines and increased temperatures. Major fish kills along the LDBR were associated with the 2018-20 drought. Independent investigations into the fish kill events concluded the root cause was insufficient water in the Darling River System to prevent the catastrophic decline in condition during dry periods. The impact of these droughts extended beyond fish communities, however, and has also had a major impact on sedentary riverine species, such as river mussels (Alathyria jacksoni).

The river mussel, Alathyria jacksoni, is a large (up to 20 cm long), long-lived (flow regime to the LDBR that are important to native fish communities. Similarly, environmental flows have the potential to reinstate important aspects of the LDBR flow regime needed for healthy mussel populations. The overall objectives of this pilot study were to carry out a baseline assessment of the likely location and abundance of Alathyria jacksoni in the LDBR after the 2018-2020 drought, and to look for indicators of mussel spawning since flows recommenced in late March 2020.

Our specific aims were to:
1. Identify and document the location of refuge pools that were likely to support remnant mussel populations in the LDBR;
2. Conduct a desktop study to estimate the potential size of the surviving adult mussel population in the LDBR;
3. Ground-truth in known refuge pools to confirm the presence/absence of adult mussels;
4. Establish if mussel spawning occurred during the 2020/21 and 2021/22 flows through the presence/absence of glochidia on fish samples; and
5. Provide recommendations for future research and environmental water delivery to support river mussels.
Original languageEnglish
Place of PublicationBuronga, NSW
PublisherNSW Department of Planning and Environment and Charles Sturt University
Commissioning bodyCommonwealth Environmental Water Office
Number of pages35
ISBN (Print)9781922840448
Publication statusPublished - Aug 2022

Grant Number

  • 10635


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