Spanish mackerel stock
Species
- Spanish mackerel (Scomberomorus commerson)
Fish stock status
Although a species may be classified as sustainable under the Status of Australian Fish Stocks (SAFS) framework, this does not mean that the stock is meeting Queensland targets under the harvest strategy.
| Stock | 2023 | 2020 | 2018 | 2016 | 2014 |
|---|---|---|---|---|---|
| East Coast | Depleted | Depleted | Sustainable | Sustainable | Sustainable |
| Gulf of Carpentaria | Depleting | Depleting | Sustainable | Sustainable | Sustainable |
Stock assessment
Spanish mackerel populations within the Gulf of Carpentaria are a separate biological stock to populations along the east coast.
These stocks are monitored and managed independently.
East coast 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.
The 2020 stock assessment used 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%.
Previous reports:
Difference to previous assessment
The 2020 assessment used Stock Synthesis, a modelling framework that was developed by the National Oceanic and Atmospheric Administration (United States). All previous assessments of this stock used models custom-built by the Queensland Department of Agriculture and Fisheries.
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. 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).
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.
Biomass estimates and key management actions
© Queensland Government
Estimated harvest from 1911 to 2020
© Queensland Government
Gulf of Carpentaria stock
Torres Strait stock
Spanish mackerel are important to the Torres Strait people and fishing culture. They are an economic and traditional food source.
The Australian Fisheries Management Authority commissioned annual updates to the Torres Strait Spanish mackerel stock assessment.
The 2022 stock assessment, conducted by Fisheries Queensland and Sea Sense, used current biological and harvest data to:
- determine the sustainability of the Spanish mackerel stock in Torres Strait waters, and to
- inform management decisions on commercial quota.
The estimated spawning biomass of Spanish mackerel in the 2021–2022 financial year (labelled as the 2022 fishing year) was 29 % of unfished levels at the start of the fishery in 1940–1941.
This stock assessment combined all estimates of Torres Strait Spanish mackerel harvest, catch rate, fish age and biological data into an annual age-structured population model.
The assessment was overseen by the Torres Strait Finfish Fishery Resource Assessment Group, a committee for the Protected Zone Joint Authority.
Previous Torres Strait report:
Biomass estimates and key management actions
Retained catch from 1940
Monitoring
The biological monitoring program collects information through the boat ramp survey on the length, sex and age of fish caught by commercial and recreational fishers.
Spanish mackerel populations within the Gulf of Carpentaria are a separate biological stock to populations along the east coast.
These stocks are monitored and managed independently.
East coast stock
The sampling is carried out along the Queensland east coast, between Cairns region and the New South Wales border. Since 2022, sampling of the commercial sector has extended north of Cairns to the Lockart region.
Data collection began in 2000 and focused on the Lucinda region until 2004, when the program was expanded to have a Queensland east coast focus. The program is ongoing.
Monitoring area
Age and length
The size ranges of Spanish mackerel harvested by both commercial and recreational sectors with most fish between 90cm to 115cm total length (TL).
The majority of fish caught by recreational and commercial fishers are around 2 to 4 years of age, however some years up to 60% of the catch can be made up of 2 year old fish. This is an indication of strong recruitment.
The oldest Spanish mackerel sampled in the monitoring program was around 26 years of age but in general fish older than 10 years are very uncommon.
Spanish mackerel have a rapid growth rate with females generally growing faster than males. Females will therefore tend to be younger than males of the same length (Graph 1).
Graph 1: Age-at-length
Gulf of Carpentaria stock
Data collection began in 2012.
Monitoring area
Age and length
The largest Spanish mackerel sampled from the Gulf across all years of the program was over 160cm total length.
Spanish mackerel are typically fully recruited into the fishery at around 2 years of age. By then the majority meet the minimum legal size of 75cm total length. Most Spanish mackerel caught by commercial and recreational line fishers are between 2 and 6 years of age. Fish older than 10 years are uncommon. The oldest Spanish mackerel sampled by the monitoring program was 15 years old.
Spanish mackerel are considered to have an initial rapid growth rate, and females generally grow faster than males. Females therefore tend to be younger than males of the same length (Graph 1). For example, a female with a total length of 107cm is typically 3 years of age with a 90% likelihood of it being between the ages of 2 and 5.
Graph 1: Age at length
Ecological risk assessment
- east coast Spanish mackerel fishery reports
- Gulf of Carpentaria line fishery reports.
Management
East coast
Torres Strait
The Torres Strait Finfish Fishery Resource Assessment Group is the research and scientific committee for management of the Torres Strait Finfish Fishery.
The group provides advice to the Protected Zone Joint Authority (PZJA) and the Torres Strait Finfish Working Group on the status of target fish stocks.
The resource assessment and working group:
- consider new stock assessments each year
- provide advice on appropriate management options for Torres Strait Spanish mackerel for the forthcoming fishing season.