Oral Presentation AFSS/NZFSS Joint Conference 2019

Quantifying links between discharge, temperature and recruitment dynamics of Murray cod to inform flow management in the southern Murray-Darling Basin (#89)

Zeb Tonkin 1 , Jian Yen 2 , Jarod Lyon 1 , Adrian Kitchingman 1 , Wayne Koster 1 , John Koehn 1 , Jason Lieschke 1 , Scott Raymond 1 , Ivor Stuart 1 , Charles Todd 1
  1. Arthur Rylah Institute, Department of Environment, Land, Water and Planning, Heidelberg, VIC, Australia
  2. School of BioSciences, University of Melbourne, Melbourne, Victoria

Verifying and quantifying links between flows and key population processes provides an evidentiary basis to support decision making and assists waterway managers to adaptively manage environmental water for fish-related outcomes. This can be relatively straightforward for species with periodic life-history strategies, which exhibit strong links to attributes of a river’s natural flow regime such as seasonal flooding. This approach can prove challenging for species which exhibit equilibrium life-history strategies, due to their long-lived nature and typically regular and stable patterns in recruitment. Indeed, in Australia’s Murray Darling Basin, there is increasing evidence that the provision of flow and flood pulses can be used to enhance recruitment for periodic species such as golden perch. However, empirical studies supporting similar recommendations for equilibrium species are rare, with many of the links between flows and recruitment dynamics still largely conceptual. This is the case even for equilibrium species such as Murray cod, which have undergone major declines and whose recovery is thought to depend on flow management. This study addresses some of the challenges associated with understanding recruitment dynamics of equilibrium fish species by using population demography data of Murray cod, collected from five rivers in the southern Murray Darling Basin over two decades. Using a novel analytical approach, we test several hypotheses linking key attributes of a river’s flow regime to recruitment dynamics. Our results are discussed in relation to flow management aimed at achieving population outcomes for Murray cod as well as species of other life-history strategies.