Barramundi (lates calcarifer) juvenile recruitment
About Lates calcarifer
L. calcarifer is a long-lived, catadromous fish species that occurs throughout northern Australia. It has been selected as an ecological asset for the Fitzroy WRP because it is a valuable commercial and recreational fishery and has a critical link to flows for the recruitment and growth of juveniles. The development of water infrastructure in the Fitzroy and the associated impacts on connectivity and water quality are known to have impacted Barramundi populations.
This model, describing the flow requirements for Barramundi juvenile recruitment, draws on the work of Sawynok and Platten (2008). There are three main flow requirements for strong recruitment: total volume of wet season flows exceed 1500 GL, the timing of the maximum flow events occur during January and February, and at least one monthly wet season flow exceeds 400 GL. In years when either the timing or the flow volume were outside this range, recruitment was found to be low (Sawynok and Platten 2008).
The purpose of the model is to analyse long times series of modelled flow to determine if the risk to juvenile recruitment of Barramundi is adversely affected by proposed water resource development for the Fitzroy River (Qld).
This model, describing juvenile recruitment of Barramundi 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.
This model and its default parameters were created for application in the Fitzroy River estuary, 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.
Juvenile Barramundi recruitment strength is dependent on the following flow parameter rules being met in a given year:
- Total volume of wet season (Nov to March) flows exceed 1500 GL
- Maximum flow events occur during January and February
- At least one monthly wet season flow exceeds 400 GL
Juvenile Barramundi recruitment strength is defined as follows:
- Strong recruitment year: all three flow parameters are met
- Moderate recruitment year: one or two flow parameters are met
- Poor recruitment year: none of the flow parameters are met
Strong recruitment years with all three flow parameters met were considered a requirement for maintaining a healthy barramundi population and the greater the number of years between these events, the higher potential risk to barramundi populations.
High-risk profile (i.e. potential local population failure) was defined as any year where the number of consecutive years without strong recruitment (all three flow parameters met) exceeded 11 years (the longevity of most barramundi).
Moderate risk profile was defined as any year where the number of consecutive years without strong recruitment was between 5 (age at sexual maturity) and 11 years.
Low risk profile was defined as any year where the number of consecutive years without strong recruitment was less than 5 years.
A binary yearly value is determined by classifying strong years successful, and all other strength as a failure. These results are then aggregated 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
- Rule 1 (Total flow volume) – parameters defining success in the total flow volume requirement. Includes the season to analyse, and the flow threshold required.
- Rule 2 (Maximum flow timing) – parameters defining success in the flow timing requirement. Includes the season in which the maximum flows should occur.
- Rule 3 (Monthly flow) – parameters defining the success in the monthly flow requirement. Includes the season in which to analyse, the number of months which need to meet the threshold and the flow threshold required.
- Intermediate assessment – parameters defining the intermediate assessment results calculated by this model. This includes the annual recruitment strength (how many rules must be met to provide string, moderate or poor recruitment) and the temporal risk (how many years without strong recruitment is high, moderate or low risk). Assessment results are still provided, separately to these intermediate assessment results.
- Yearly time series of rule success, recruitment strength and risk.
- Temporal time series of assessment results (This is seperate to the temporal risk which is included in the yearly intermediate results)
- Spatial time series of assessment results
This plugin is written in Python and its underlying code is publicly available from the Eco Risk Projector computation repository.
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.
Sawynok W and Platten J 2008, ‘Use of 12 Mile Creek by Barramundi: Effects of Local Climate 1984-2007’, Infofish Services.