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Ambassiz’s glassfish (Ambassis agassizii)

About Ambassis agassizii

Ambassis agassizii (Agassiz’s glassfish. Other names: olive perchlet, Agassiz’s perchlet, glassfish, glass perchlet, western chanda perch) is a small-bodied fish that inhabits freshwater systems in the Murray-Darling Basin and the east coast of Australia.

It was selected as an ecological asset for the Fitzroy Basin Water Resource Plan because it has a critical link to flows for the provision of spawning and recruitment opportunities and is deemed to be potentially at risk from changes to the flow regime.

Water requirements

A. agassizii requires stable low flows for recruitment. A rise in water temperature is required to stimulate spawning, a stable water level is required for successful egg development and a slow rate of water level change is required for larval growth. Opportunities for successful recruitment are likely to be at greatest risk from rapid changes in water level, due to flow management. Water levels that are too high or too low may result in a loss of spawning and nursery habitat, and water levels that fall too rapidly may result in the exposure and desiccation of eggs, as well as greater rates of predation on eggs and larvae due to exposure (Pusey et al. 2004). Additionally, disruption to post-larval development flows may prevent juvenile fish migrating to nursery habitats such as floodplains and upland pools. In managed river networks, rapid water level changes may result from either water extraction or flow supplementation. At the population scale, any reduction in annual number of recruitment opportunities may influence the long-term resilience and subsequent viability of the species.

Model purpose

The purpose of the model is to assess the long term population viability of A. agassizii in the Fitzroy Basin.

Development context

This model, describing the flow requirements for spawning and egg and larval survival, has been developed using quantitative information from the literature and expert opinion (see Cockayne et al 2010).

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

Spatial application

This model and its default parameters were created for application in the Fitzroy Basin, Queensland.

However, the model parameters could be edited to suit other locations or species with similar requirements.

Model description

Ecohydrological rules

A recruitment opportunity is defined as:

  • daily discharge ≤ median daily flow
  • water temperature > 22° (or it is within the defined spawning season of September- December) and
  • water level remains ±5cm of starting level for 7 days for eggs and then
  • water level changes by <5cm per day for 20 days for larvae

Because A. agassizii 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.

Assessment Methods

This model produces binary daily results (daily spawning success). 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.

Inputs

Data
  • Daily depth data – required
  • Daily flow data – optional
  • Daily temperature data – optional (if not loaded the seasonal start and end is used for every year)
Parameter Sections
  • Lowflow – define the lowflow requirement. Either a set threshold or the median flow across the time series.
  • Breeding Season – define the breeding season, which lowflow much occur in. Either a set season between dates, or based on temperature if the 7 day moving average of temperature exceeds a set threshold.
  • Life Stages Criteria (Egg) – define egg success, given breeding success. A total max change in depth, across a set number of days.
  • Life Stages Criteria (Larvae) – define larvae success, given egg success. A max daily change in depth, across a set number of days following the egg criteria days.

Outputs

  • Daily time series of recruitment success, including intermediate results such as if the day is in breeding season, if the flow threshold is not exceeded, if there is suitable time to complete the event (enough days to check egg and larvae criteria), the egg criteria success and finally the larvae criteria success.
  • 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.

References

Bray, D.J. & Thompson, V.J. 2018, Ambassis agassizii in Fishes of Australia, accessed 18 Oct 2022, https://fishesofaustralia.net.au/home/species/1581

Cockayne B, McGregor G, Marshall J, Lobegeiger J, and Menke N 2010, ‘Fitzroy Water Resource Plan review technical report 3: ecological risk assessment’, Department of Environment and Resource Management, Queensland Government, Brisbane.

Pusey, Bradley J. & Kennard, Mark J. & Arthington, A. H. & CSIRO Publishing. & Griffith University. Centre for Riverine Landscapes.  (2004).  Freshwater fishes of north-eastern Australia.  Collingwood, Vic :  CSIRO Pub