Linking flow attributes to recruitment to inform water management for an Australian freshwater fish with an equilibrium life-history strategy Zeb Tonkin a, ⁎, Jian Yen a,b , Jarod Lyon a , Adrian Kitchingman a , John D. Koehn a , Wayne M. Koster a , Jason Lieschke a , Scott Raymond a , Joanne Sharley a , Ivor Stuart a , Charles Todd a a Applied Aquatic Ecology, Arthur Rylah Institute for Environmental Research, Department of Environment, Land, Water and Planning, 123 Brown Street, Heidelberg, Victoria 3084, Australia b School of BioSciences, University of Melbourne, Melbourne, Victoria 3010, Australia HIGHLIGHTS • Flow-recruitment relationships for equilibrium fish species are poorly quantified. • Murray cod recruitment measured over 2 decades in rivers varying in flow regu- lation. • Recruitment linked to several flow attri- butes but often river-specific. • Simulating natural flow regimes en- hances native fish recruitment in regu- lated rivers. • This analysis can be applied to other species sharing life-history strategies. GRAPHICAL ABSTRACT abstract article info Article history: Received 15 April 2020 Received in revised form 10 August 2020 Accepted 19 August 2020 Available online 23 August 2020 Editor: Sergi Sabater Keywords: River regulation Environmental flows Murray cod Murray-Darling basin Australia Bayesian Natural flow regime Recognition that many species share key life-history strategies has enabled predictions of responses to habitat degradation or rehabilitation by these species groups. While such responses have been well documented for freshwater fish that exhibit ‘periodic’ and ‘opportunistic’ life-history strategies, this is rare for ‘equilibrium’ life-history, due largely to their longevity and by comparison, more regular and stable levels of recruitment. Un- fortunately, this limits the confidence in using life-history strategies to refine water management interventions to rectify the negative impacts of river regulation for these species. We addressed this knowledge gap for Murray cod Maccullochella peelii, a high-profile, long-lived recreationally popular equilibrium species in south-eastern Australia. We used monitoring data collected across a gradient of hydrologically altered rivers over two decades, to test various hypotheses linking recruitment strength with key attributes of the flow regime. Although Murray cod recruited in most years, as expected for an equilibrium species, responses to flow varied among and within rivers among years. We found links between recruitment strength and the magnitude and var- iation in discharge during the spring spawning period, as well as flows experienced by juvenile fish during sum- mer and winter - the hydrological components most affected by river regulation. However, the specific slopes and directions of some of these links varied idiosyncratically across rivers. Our results emphasise the importance of accounting for flows that influence each of the key life stages during the recruitment process and lend support for managing rivers in accordance with the natural flow regime. It also shows the need for waterway-specific studies and further refinement of existing flow metrics to allow more credible transferability of results. The approach used in this study can also be applied to other species sharing life-history strategies for which long-term monitoring data has been compiled and length-at-age relationships established. Crown Copyright © 2020 Published by Elsevier B.V. All rights reserved. Science of the Total Environment 752 (2021) 141863 ⁎ Corresponding author at: PO Box 137, Heidelberg, Victoria 3084, Australia. E-mail address: Zeb.Tonkin@delwp.vic.gov.au (Z. Tonkin). https://doi.org/10.1016/j.scitotenv.2020.141863 0048-9697/Crown Copyright © 2020 Published by Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv