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Superseded – Australian bass (Macquaria novemaculeata) spawning and juvenile movement

About Macquaria novemaculeata

Australian Bass (Macquaria novemaculeata) are a high value target species for environmental flow assessment. The fish is primarily a freshwater species, but they migrate downstream to spawn in estuaries. They are found in coastal rivers of the east coast of Australia (south of the Mary River in Queensland). Migration and breeding generally occurs between May and August.

A general description of the typical migratory pattern for adult Australian bass in the central (NSW) portion of their range would be:

  • May: strong spawning run to estuarine reaches
  • June–July–August: aggregation and spawning in estuarine reaches
  • September: re-enter lower freshwater reaches after spawning
  • October–November: movement through middle freshwater reaches
  • December–February: maximum penetration into negotiable upper freshwater reaches
  • March–April: slow movement back down through freshwater reaches in anticipation of spawning run

This model was developed for consideration of environmental water requirements in the Hawkesbury-Nepean River system.

Water requirements

Australian Bass (Macquaria novemaculeata) requires suitable flow conditions to allow downstream migration to estuaries to spawn, and upstream movement of juveniles. Australian Bass adults move downstream to the estuary to spawn based on a combination of cool water conditions (<15Degrees) and a flow movement trigger. Additionally, movement may be restricted by passage through shallow areas such as Bishops Bench (Hawkesbury Nepean River). Return upstream of juvenile Bass does not require a flow trigger or temperature controls but may be controlled by a minimum depth or velocity over shallow areas such as bishops bench (Hawkesbury Nepean River).  It is expected that this plug in would be used to construct separate models for both adults downstream movement and juvenile upstream movement. This model uses a flow or depth time series along with a user defined trigger of suitable movement conditions (separate triggers for commencement and end of suitable conditions). For every day of the input time series the model creates a score of suitability for movement based on the commencement triggers, the water temperature or time of year and if critical conditions for movement have been achieved. The model takes the minimum of these three criteria to allocate a daily suitability score (0-1). Higher model scores indicate better spawning or juvenile recruitment opportunities. [/av_textblock] [av_textblock textblock_styling_align='' textblock_styling='' textblock_styling_gap='' textblock_styling_mobile='' size='' av-desktop-font-size='' av-medium-font-size='' av-small-font-size='' av-mini-font-size='' font_color='' color='' id='' custom_class='' template_class='' av_uid='av-l9ddbejj' sc_version='1.0' admin_preview_bg='']

Model purpose

The purpose of the model is to assess the long term population viability of Australian bass (Macquaria novemaculeata) in the Hawkesbury Nepean River system.

Development context

This model, allows for the comparison of the frequency and duration of spawning trigger events and the frequency and duration of adequate depth of critical shallow areas such as Bishops Bench in the Hawkesbury- Nepean River system.

It was developed to support the New South Wales Government water resource assessment process in the Hawkesbury- Nepean River system.

Spatial application

This model and its default parameters were created for application in the Hawkesbury- Nepean River system in New South Wales.  However, the model may be applied more broadly as the Australian Bass are found in fresh and saltwater, in eastern draining rivers from the Mary River in Queensland to the Gippsland Lakes in Victoria.

Model description

Ecohydrological rules

A recruitment opportunity is defined as:

  • Water temperature < 15° (or it is within the defined spawning season) and
  • Flow exceeds the 90th percentile flow (to allow downstream migration).
  • Flow exceeds the 50th percentile to allow upstream movement of juveniles after successful spawning conditions.
  • Depth exceeds the provided depth threshold (1) – only if depth data is provided. This is vital to assess critical conditions for passage through bishops bench.

Assessment method

This model produces continuous daily results (number of daily spawning successes in a row). These results are then aggregated to a binary daily result, then to a binary yearly result, and then further to a binary temporal result based on the defined assessment parameters.

The temporal results are then analysed across locations to report an overall landscape risk by considering the simultaneous occurrence of failures across the system.


  • Daily flow data
  • Daily depth data (optional)
  • Daily temperature data (optional)
Parameter Sections
  • Commence to move triggers – a user defined threshold for the commencement and end of the movement period, can relate to flow or depth input time series. The end threshold should be smaller than the start threshold.
  • Flow parameters – Parameters to define the commencement and end of the movement period. Can use flow percentiles or just specify threshold values. Can provide a depth threshold to be used if depth data is provided.
  • Season – The period to check for success. Can be based on the provided temperature threshold (all days with a 7-day moving average temperature below the threshold are in season, required temperature data) or just defined by a date range.


  • Daily time series of suitable conditions, a score of 1 applies for periods when movement is possible and a score of zero when no movement is possible. Days of continuous movement are captured by a running total of success (I.E. the third successful day in a row will have a success of 3)
  • Daily time series of assessment results
  • Yearly time series of assessment results
  • Temporal time series of assessment results
  • Spatial time series of assessment results

User interface

Underlying code

This plugin is written in Python and its underlying code is publicly available from the Eco Risk Projector computation repository.