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Catfish (Tandanus tandanus) Trigger for nest construction and egg survival

About Tandanus tandanus

The eel-tailed catfish (Tandanus tandanus) is a medium-sized, benthic pool dwelling fish endemic to Australia. Breeding occurs between spring and mid-summer when water temperatures rise. This species is widespread throughout coastal and inland drainages of eastern Australia, ranging from Cape Tribulation in the Wet Tropics region of northern Queensland, south to Shoalhaven River in central New South Wales (Pusey et al. 2004). The eel-tailed catfish occurs in all catchments within the Wet Tropics water plan area, except for the Herbert, and has received little formal recognition as a threatened species despite its declining distribution and abundance, particularly in southern Australia. The eel-tailed catfish has been selected as an ecological asset for the Wet Tropics water plan area due to the importance of stable low-flows for spawning and recruitment success.

Water requirements

This model, describing the flow, temperature and depth requirements for nest development and persistence of stable flow conditions for egg survival. This model has been developed using quantitative information from the literature and expert opinion (see Cockayne et al 2010).

The eel-tailed catfish has three water flow requirements and one temperature requirement for a successful breeding year. Firstly, nest construction and spawning in this species are thought to be triggered by rising maximum daily water temperatures in spring and summer (Pusey et al. 2004). As habitat-specific spawners, a majority of nest construction also occurs within a specific water depth range. Successful spawning and egg development requires stable low-flows for at least 30 days from the time of spawning to prevent washout or desiccation, allowing time for development of free-swimming larvae.

Model purpose

The purpose of the model is to analyses long times series of modelled flow to determine if the risk to successful breeding events for eel-tailed catfish is adversely affected by proposed water resource development (represented in the modelled flow).

Development context

This model, describing flow requirements for successful spawning of Tandanus tandanus, has been developed using quantitative information from the literature and expert opinion.

It was developed to support the Queensland Department of Environment and Resource Management’s ecological risk assessment for Water Resource Plan (WRP) reviews.

Spatial application

This model and its default parameters were created for application in the Wet tropics water resource plan area, Queensland.

However, the model parameters could be edited to suit other locations where Tandanus tandanus, occurs.

Model description

Ecohydrological rules

A recruitment opportunity is assumed to have occurred if daily flows were low and stable (≤ median daily flow and within upper and lower depth bounds), and those flows coincided with suitable water temperatures (above the minimum spawning temperature) or occurred within the spawning season, and water levels remained stable for the duration of egg and larval development. That is, when the following parameters are met:

  • Water temperature > 22° (or it is within the defined season)
  • Low flow – (either discharge or velocity) remains at or below the threshold for 30 consecutive days
  • Stable flow – water level is within (or equal to) the upper and low depth bounds and stays above the critical desiccation threshold for 30 continuous days. The lower depth bound is assumed to be the desiccation threshold.

Because eel-tailed catfish are serial spawners and different females within a local population can lay eggs at different times, there is a moving window of overlapping recruitment opportunity (it does not necessarily represent the total number of spawning events).

Assessment methods

This model produces binary daily results (daily recruitment opportunities). These results are then aggregated to a yearly result, and then further to a 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
  • Season – the season to analyse. This can be defined through dates or by a temperature threshold (when the temperature is above the threshold, it is in season)
  • Flow parameters – the flow related requirements. This includes the flow threshold (can also be defined as an ARI), the duration and the depth range. The depth range is only considered on days where depth data is provided.


  • Daily time series of recruitment opportunities, including additional intermediate results. These include if the day is in season, if there is suitable time to complete the event, if the flow threshold is not exceeded during the period and it the depth stays in the depth range during the period.
  • 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.


Pusey B, Kennard M & Arthington A. 2004. Freshwater fishes of North Eastern Australia. CSIRO Publishing, Australian Government, Collingwood.