Fish and Flows in the Murray River Catchment


In developing the Murray-Darling Basin Plan, the Murray–Darling Basin Authority (MDBA) used an indicator site method to assess the environmental water needs of the MDB using the best science available at the time (2009).

DPI Fisheries (NSW) in partnership with the Arthur Rylah Institute (ARI) were contracted by the MDBA to undertake a review of the information available (as of 2015) regarding the flow requirements of fish in the Southern MDB.

Key advances in our understanding of fish and flow relationships since 2009 include:

  • The importance of hydrodynamic complexity (i.e. the distribution and change in velocity, depth, turbulence) in supporting life cycles and diversity within fish communities.
  • The linkages between flow requirements and the different life history stages of fish.
  • The spatio-temporal scales at which habitat and population processes occur (e.g. annual processes occurring within localised habitats compared to processes which occur over 100’s or 1000’s of km spanning multiple years).
  • The importance of unobstructed connectivity (between channels and floodplains, and also between locations and catchments), and translucency of flows to fish condition, recruitment, movement and population dynamics.
  • How hydrological variability influences riverine productivity, which in-turn promotes food and breeding opportunities for within-channel fishes (i.e. the links between flow, growth, body condition and recruitment success).
  • The influence of antecedent hydrology on fish assemblages, and hence the importance of sequential flows in supporting healthy populations (e.g. growth, body condition and recruitment success).
  • How floods and in steam flows may augment recruitment; infrequent overbank flooding interspersed with within-channel increases in discharge may result in more frequent spawning and recruitment (trickle recruitment) and more robust population structure.
  • That negative outcomes may arise from managed flow regimes (e.g. increased risk of non-native fish recruitment, hypoxic blackwater events and sedimentation).
  • That the extent of water and land use in the MDB may mean there is a need for complementary actions in addition to the delivery of optimal flow regimes to achieve meaningful outcomes for native fish.

The information synthesised in the review of fish and flow relationships was then used to develop a framework to apply this knowledge. In this document we formulate an approach that will support decision making in the application of environmental water for fish.

It is anticipated the outputs of this project will assist agencies with environmental water management responsibilities in the implementation of Murray–Darling Basin Plan.

Responsible water management and the prioritisation of hydrograph requirements within and between systems (both spatially and temporally) will require coordinated efforts by water managers across both the Southern and Northern MDB, and sustained consultation with expert fish ecologists.

The framework presented here will be trialled through monitoring and evaluation of Basin Plan Implementation over the next 5 years. Knowledge gained will contribute to improved adaptive management of native fish into the future.


Some of the content in the downloadable report does not comply with WCAG 2.0 accessibility requirements. To obtain accessible versions of graphs and other data contact:

Iain Ellis
Fisheries Manager, Aquatic Habitat Rehabilitation


Published: Jul 2016