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Queensland offshore reef fishery

About Offshore Reef fishery

The offshore reefs adjacent to the Fitzroy catchment are home to a variety of fish species and other marine life. As such, the area is a popular site for recreational fishing and associated tourism activities. The fisheries of offshore reefs have been selected as an ecological asset for the Fitzroy Water Resource Plan because they have a critical link to flows, which are known to boost recreational catch rates, and are deemed to be potentially at risk from changes to the flow regime.

Water requirements

This model is based on the work of Platten and Sawynok (2008), which used long-term catch data from recreational fishing clubs in the Capricorn region to develop predictive models of offshore fisheries’ response to river flow.

Model purpose

The purpose of the model is to analyses long times series of modelled flow to determine if the risk to the Queensland offshore reef fishery is adversely affected by proposed water resource development for the Fitzroy River (Qld).

Development context

This model, describing Queensland offshore reef fishery is based on an empirical model developed for the Fitzroy River Catchment. It was developed to support the Queensland Department of Environment and Resource Management’s ecological risk assessment for the Fitzroy River Water Resource Plan (WRP) reviews.

Spatial application

This model and its default parameters were created for application in the Fitzroy River, Queensland. However, the model parameters could be edited to suit other locations if the underlying observation data exists to create a model of the same form.

Model description

Ecohydrological rules

High annual freshwater flow to the Fitzroy River Estuary are correlated to high catch rates in the following year. Catch rate (from Platten and Sawynok 2008) is predicted by a numerical model of two parts to represent the relationship between flow and catch, and the lagged effect of high-flow years which lead to higher catch in the following year. The first model is a logistic equation and includes all years, apart from those following high flow years, and is of the form:

Catch rate = f/(a+b.e^ -((m(wet season flow)+c)/g))+d

Using the constants:

a b c d f m g
12120.44 3312455.74 -210028.55 16.53 190548.16 1.08 1083205.75

The second model includes only years following high flow years and is of the form: Catch rate following high flow year = 0.6473x + 40969 (R2 = 0.89)

where x is the catch rate in the preceding high flow year

Assessment method

This model produces continuous yearly results (reef fish catch rate). These results are then aggregated 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
Parameter Sections
  • Constants – define the constants to be used by the catch rate equation. Includes all constant parameters as described above.
  • Flow parameters – define the flow parameters used to determine if a year is a high flow year. Includes season to determine year, and flow threshold to determine a high flow year.


  • Yearly time series of catch rate and if the high flow threshold was met
  • 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.


Sawynok W and Platten J 2008, ‘Use of 12 Mile Creek by Barramundi: Effects of Local Climate 1984-2007’, Infofish Services.