Standard Talk (15 mins) Australian Society for Fish Biology Conference 2022

A Tale of Two Sities [sic]: Long-term Patterns of Fish Communities at Lindsay-Mulcra-Wallpolla and Hattah Lakes, Lower Murray River. (#108)

Alison King 1 , Luke McPhan 1 , Chris Bloink 2 , Bryce Halliday 2 , David Wood 3 , Emma Collins 3 , Sam Lewis 1
  1. Centre for Freshwater Ecosystems, La Trobe University, Albury-Wodonga, Vic, Australia
  2. Ecology Australia, Fairfield, VIC, Australia
  3. Mallee Catchment Management Authority, Mildura, VIC, Australia

The Lindsay-Mulcra-Wallpolla (LMW) and Hattah Lakes (HL) Icon Sites are part of The Living Murray (TLM) Condition Monitoring Program. The TLM condition monitoring program aims to measure the long-term ecological benefits of environmental flows and other management activities at Icon Sites along the Murray River. Condition monitoring has been undertaken annually since 2006, with the exception of 2015, due to a lack of program funding. Since 2010, fish monitoring has occurred in Autumn at fixed sites, stratified by macrohabitats within each Icon Site: Riverine, Anabranch, Channel (LMW only) and Wetland (HL only). Fish sampling uses standardised methods and effort, including: electrofishing (boat/backpack), seine hauls and fyke nets. All fish collected are identified, measured and returned to the water. The aim of this project was to undertake a range of analysis approaches to explore (i) population differences among years and macrohabitats, (ii) long-term population trends and change-points, and (iii) the influence of suspected key drivers of population changes.

Although derived from the same species pool, fish communities at LMW and HL are remarkably different between the Sites, among macrohabitats, and have exhibited significant shifts due to higher flows and drying periods. The presence and abundance of large-bodied native species has undergone distinct periods of fluctuations due to the effects of blackwater (2011, 2016), high flows (2010–12, 2016, 2022) and low flow/dry years (<2010, 2014–16, 2017–21). There are also key differences in species responses given their life history attributes. The abundance of common small-bodied native species fluctuates significantly across years, while many other small-bodied species remain at low or sporadic detection. This analysis describes important variability in fish communities and establishes a baseline to set realistic future restoration targets for native fish in the region.