Spanish mackerel stock assessment
Chart of 2020 Australian east coast stock assessment biomass estimates and key management actions for Spanish mackerel
© Queensland Government
Chart of estimated harvest for Queensland east coast Spanish mackerel from 1911 to 2020
© Queensland Government
Why did we assess the Spanish mackerel stock?
There have been longstanding concerns about the sustainability of Spanish mackerel on the east coast of Queensland. Scientific research also included evidence of reduced catch rates and loss of spawning aggregations.
In 2020, Fisheries Queensland completed a stock assessment using the most current biological data, and commercial and recreational catch data to:
- determine the sustainability of fish stocks
- inform management decisions.
- inform the development of a harvest strategy.
This assessment estimated that the number of Spanish mackerel (biomass) was between 14% and 27% of unfished levels, and most probably at around 17%.
Why were the 2020 results different to past assessments?
The 2020 assessment used a stock assessment model called Stock Synthesis, one of the most widely used and tested stock assessment models in the world and is currently used by CSIRO and other Australian fisheries jurisdictions.
The 2020 stock assessment included more up-to-date data on recreational and commercial harvests, as well as new biological data such as fish length and age. All previous stock assessments (2001, 2007, 2009 and 2016) used models custom built by DAF. The new data included:
- recreational catch and effort from 4,692 diary events (fishing trips) from the 2019–2020 Statewide Recreational Fishing Survey
- commercial catch and effort (including an additional 16,055 fishing days)
- biological data (including 15,813 additional length data and 2,993 additional age data).
Findings from the independent review
As best practice, Fisheries Queensland conducts independent reviews of stock assessments and other scientific reports on a regular basis.
An independent review of the Spanish mackerel stock assessment was conducted by Dr Neil Klaer, a former CSIRO fisheries scientist. The reviewer agreed the data was used appropriately in the assessment and that the assessment model itself was suitable. The reviewer questioned the model setting for lower resilience in the ability for Spanish mackerel as a species to bounce back after high fishing pressure and was unable to support model predictions until this uncertainty was resolved.
The stock assessment, the independent review and the department’s response to the review were noted by the independent Sustainable Fisheries Strategy Expert Panel. The independent panel commented that, while the reviewer’s findings were justified, the department’s response was defensible. Given this, the independent panel considered the most responsible way forward is to accept the stock assessment as the most credible scenario, and make management decisions accordingly.
The finalised assessment estimated the 2020 biomass was between 14% and 27% of unfished levels, and most probably at 17%.
Next steps for fishery management
Under the Queensland Harvest Strategy Policy, rebuilding strategies are required for stocks below 20% biomass. The first preference is to rebuild the stock with restricted targeted fishing, providing it can be achieved within a specified timeframe. However, if this cannot be achieved, fishing for the affected species may be ceased for a period.
A Spanish mackerel working group has been formed to provide advice on the management of the Spanish mackerel fishery and includes representatives from commercial, recreational and charter fishing sectors, environment groups, and the Great Barrier Reef Marine Park Authority.
The working group will:
- provide advice on appropriate management action to rebuild the Spanish mackerel fishery
- develop a rebuilding harvest strategy for this fishery consistent with the principles of the Sustainable Fisheries Strategy 2017–2027.
Broad public consultation is planned for 2022 to allow all stakeholders, including commercial, recreational, charter and traditional fishers, environmental groups and other interested stakeholders, to provide comments to inform a final decision on management action to rebuild this important fishery.
More information
Access the Stock assessment of Australian east coast Spanish mackerel report, review and response to the review.