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Grey Mackerel (2023)

Scomberomorus semifasciatus

  • Marlee Jesson-Kerr (Department of Agriculture and Fisheries, Queensland)
  • Paul Lewis (Department of Primary Industries and Regional Development, Western Australia)
  • Michael Usher (Department of Industry, Tourism and Trade, Northern Territory)

Date Published: June 2023

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Summary

The five stocks of Grey Mackerel assessed across Australia’s northern waters are all sustainable.

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Stock Status Overview

Stock status determination
Jurisdiction Stock Stock status Indicators
Northern Territory Gulf of Carpentaria Sustainable

Catch-MSY modelling, nominal catch rate, effort distribution, risk profile

Northern Territory North West Northern Territory Sustainable

Biomass, fishing mortality, catch, catch rate

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Stock Structure

Grey Mackerel (Scomberomorus semifasciatus) are found in southern Papua New Guinea and northern Australia from Shark Bay, Western Australia, to northern New South Wales. At least five Grey Mackerel stocks have been identified for management purposes across northern Australia as determined by otolith stable isotopes chemistry and parasite abundance: Western Australia, North West Northern Territory, Gulf of Carpentaria, East Coast North and East Coast South. Four of these stocks have been confirmed as genetically distinct biological stocks: Western Australia, North West Northern Territory, Gulf of Carpentaria and the East Coast of Queensland. Research suggests that a sixth stock potentially occurs in the north-east Gulf of Carpentaria [Welch et al. 2009; Charters et al. 2010; Newman et al. 2010; Broderick et al. 2011; Welch et al. 2015]. However, the presence of this stock has yet to be confirmed; therefore, it was not included in the assessment.

Here, assessment of stock status is presented at the biological stock level—Western Australia, North West Northern Territory, Gulf of Carpentaria, and at the management unit level for North East Queensland and South East Queensland.

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Stock Status

Gulf of Carpentaria

Grey Mackerel in the Gulf of Carpentaria is primarily a commercial gillnet-caught species. Over 90% of the reported catch was captured by Queensland operations (2021–22 data). The majority of the remaining catch is reported from the Northern Territory by operators in the Offshore Net and Line Fishery (ONLF).

In Queensland, the 2021–22 Grey Mackerel catch of 987 tonnes (t) was the highest recorded and exceeded the 10-year average of 657 t (2011–12 to 2020–21). However, effort in the Queensland region has shown a decreasing trend from 2017–18, dropping from 1,276 to 827 annual fishing days in 2021–22, the lowest recorded since 1995–96. The nominal catch rate has shown an increasing trend, however due to difficulties in distinguishing effort from co-targeted species, the trend is uncertain. The Queensland Grey Mackerel effort footprint appears to have contracted over 2017 to 2021 with operations focusing more on northern Gulf regions. Although some effort may have shifted in response to the introduction of marine park closures in 2018 [Parks Australia 2018], the reasons behind the recent shift northward are not certain and it is difficult to ascertain if this is driven by operational/economic considerations or due to changes in regional biomass levels. However, it is notable that this region is a possible additional management unit (distinct adult stock) due to differences in parasite abundance [Welch et al. 2015], which suggests that concentrated fishing in this area could contribute to localised depletion in the long term. Particularly noting that grey mackerel aggregating behaviour makes them more susceptible to targeted fishing pressure [Pidd et al. 2021].

Outside of commercial fishing, the fishing pressure exerted on Grey Mackerel by other sectors in the Gulf of Carpentaria is limited. Recreational catch for this stock is likely to be low, with the species registering combined state-wide catch of 16 t [Teixeira et al. 2021]. Grey Mackerel catch rates in the charter sector are unknown but thought to be low in Queensland. Charter vessels in the Northern Territory recorded less than 1 t of Grey Mackerel catch in 2021–22. 

While there is no recent assessment of the risk of the fishery on Grey Mackerel in the Gulf of Carpentaria, a 2021 Ecological Risk Assessment (ERA) assessed Grey Mackerel as medium risk on the east coast of Queensland and aspects of the assessment such as life history traits would apply to all stocks [Pidd et al. 2021]. The ERA suggested grey mackerel have life history traits that are highly productive, including low age at maturity, high fecundity, and a broadcast spawning reproductive strategy [Pidd et al. 2021]. Productive species may be more resilient to higher fishing pressure; however Grey Mackerel on the east coast of Queensland are susceptible to hyperstability due to predictable aggregating behaviour [GBRMPA 2012], which may make this species more susceptible to targeted fishing pressure in the Gulf of Carpentaria. 

Grey Mackerel catch in the Gulf of Carpentaria (Queensland and Northern Territory data) was subject to a catch-MSY model-assisted catch-only assessment based on catch data to 2021 [Martell and Froese 2013]. This analysis detected a declining trend in regional Grey Mackerel biomass. However, the model also indicated that biomass levels were more than likely above the reference limit point in 2021 [Northern Territory Government, unpublished]. The analysis also suggests fishing mortality is more likely to be below the limit reference point, although mortality was estimated to show an increasing trend [Northern Territory Government, unpublished]. This indicates that the current level of fishing is unlikely to cause the stock to become recruitment impaired in the short-term. However, the assessment estimated that recent harvests have exceeded FMSY and are beyond that which would be considered sustainable in the long term. The notable caveat being that catch-MSY modelling has a higher degree of uncertainty and should not be solely relied on to make inferences about long-term biomass trends. The above evidence indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. 

On the basis of the evidence provided above the Gulf of Carpentaria biological stock is classified as a sustainable stock.

North West Northern Territory

Grey Mackerel in the North West Northern Territory stock are primarily taken in the NT Offshore Net and Line Fishery (ONLF) using pelagic gillnets. Grey Mackerel harvest in the ONLF is restricted within a species-specific total allowable catch limit, which is managed through an individual transferable quota system.

Previous assessments of this biological stock included historic catch attributed to the Taiwanese gillnet fleet that operated in Northern Australia from 1974 to 1986. This historic catch was excluded from the most recent assessment, as it is unlikely the Taiwanese fleet encountered this species due to the offshore nature of the fleet’s operations and the coastal nature of Grey Mackerel populations. 

The most recent assessment using data to 2021 estimates that the biomass in 2021 was 74% of the unfished level and that the harvest rate was 54% of that required to achieve MSY [North Territory Government, unpublished]. The stock is not considered to be recruitment overfished and the current level of fishing mortality is unlikely to cause the stock to become recruitment impaired.

On the basis of the evidence provided above, the North West Northern Territory biological stock is classified as a sustainable stock.

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Biology

Grey Mackerel biology [Cameron and Begg 2002]

Biology
Species Longevity / Maximum Size Maturity (50 per cent)
Grey Mackerel

14 years, 1,200 mm FL 

Females 2 years, 650–700 mm FL Males 1–2 years, 550–600 mm FL
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Distributions

Distribution of reported commercial catch of Grey Mackerel
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Tables

Fishing methods
Northern Territory
Commercial
Gillnet
Unspecified
Charter
Hook and Line
Indigenous
Hook and Line
Recreational
Hook and Line
Management methods
Method Northern Territory
Charter
Gear restrictions
Possession limit
Spatial closures
Commercial
Fishery spatial closures
Gear restrictions
Quota
Spatial zoning
Total allowable catch
Vessel restrictions
Indigenous
No limits on customary catch
Recreational
Gear restrictions
Possession limit
Spatial closures
Catch
Northern Territory
Commercial 488.64t
Charter 1.4 t in FTO
Indigenous Unknown
Recreational 11 t ( 3,722 fish, se +/- 1,436; 2018–2019)

Western Australian – Recreational (catch). Western Australian boat-based recreational catch survey from 1 Sep 2017–30 Aug 2018 [Ryan et al. 2022]. Shore based recreational catch (if any) largely unknown.

Western Australia – Recreational (Management methods). Western Australian boat-based recreational licence required.

Northern Territory – Charter (management methods). In the Northern Territory, charter operators are regulated through the same management methods as the recreational sector but are subject to additional limits on license and passenger numbers.

Northern Territory - Indigenous (management methods). The Fisheries Act 1988 (NT), specifies that: “Unless expressly provided otherwise, nothing in this Act derogates or limits the right of Aboriginal people who have traditionally used the resources of an area of land or water in a traditional manner to continue to use those resources in that area in that manner.”

Queensland – Indigenous (management methods). For more information see: https://www.daf.qld.gov.au/business-priorities/fisheries/traditional-fishing

Queensland – Recreational Fishing (Catch). Data based at the whole of Queensland level and derived from state-wide recreational fishing surveys. Where possible, estimates have been converted to weight (tonnes) using best known conversion multipliers. Conversion factors may display regional or temporal variability. In the absence of an adequate conversion factor, data presented as number of fish. 

Queensland – Commercial (Catch). Queensland commercial and charter data has been sourced from the commercial fisheries logbook program. Further information available through the Queensland Fisheries Summary Report at: https://www.daf.qld.gov.au/business-priorities/fisheries/monitoring-research/data/queensland-fisheries-summary-report

Queensland – Commercial (Management Methods). Harvest strategies are available at: https://www.daf.qld.gov.au/business-priorities/fisheries/sustainable/harvest-strategy  

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Catch Chart

Commercial catch of Grey Mackerel - note confidential catch not shown
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References

  1. Bessell-Browne, P, Lovett, R, Leigh, G, O'Neill, MF and Campbell, A, 2019, Stock assessment of the Australian east coast grey mackerel (Scomberomorus semifasciatus) fishery, Technical Report, State of Queensland.
  2. Broderick, D, Ovenden, J, Buckworth, R, Newman, S, Lester, R and Welch, D 2011, Genetic population structure of grey mackerel Scomberomorus semifasciatus in northern Australia, Journal of Fish Biology, 79: 633–661.
  3. Cameron, D and Begg, G 2002, Fisheries biology and interaction in the northern Australian small mackerel fishery, final report to Fisheries Research and Development Corporation, projects 92/144 and 92/144.02, Department of Primary Industries, Queensland.
  4. Charters, R, Lester, R, Buckworth, R, Newman, S, Ovenden, J, Broderick, D, Kravchuk, O, Ballagh, A and Welch, D 2010, The stock structure of grey mackerel Scomberomorus semifasciatus in Australia as inferred from its parasite fauna, Fisheries Research, 101: 94–99.
  5. Great Barrier Reef Marine Park Authority, 2011, A vulnerability assessment for the Great Barrier Reef - Grey mackerel.
  6. Great Barrier Reef Marine Park Authority, 2012, A vulnerability assessment for the Great Barrier Reef: Grey Mackerel, Vulnerability Assessments for the Great Barrier Reef, Ecosystems, Great Barrier Reef Marine Park Authority.
  7. Lewis PD, 2020, Statewide Large Pelagic Resource in Western Australia, Resource Assessment Report No 19, Department of Primary Industries and Regional Development Western Australia, 145pp.
  8. Martell, S and Froese, R, 2013, A simple method for estimating MSY from catch and resilience, Fish and Fisheries, 14(4), pp 504-514.
  9. Newman, S, Wright, I, Rome, B, Mackie, M, Lewis, P, Buckworth, R, Ballagh, A, Garrett, R, Stapley, J, Broderick, D, Ovenden, J and Welch, D 2010, Stock structure of grey mackerel, Scomberomorus semifasciatus (Pisces: Scombridae) across northern Australia, based on otolith isotope chemistry, Environmental Biology of Fishes, 89: 357–367.
  10. Newman, SJ, Wise, BS, Santoro, KG and Gaughan, DJ (eds) 2023, Status Reports of the Fisheries and Aquatic Resources of Western Australia 2021/22: The State of the Fisheries, Department of Primary Industries and Regional Development, Western Australia.
  11. Northern Territory Government 2012, Fishery Status Reports 2011, Fishery Report 111, Northern Territory Government.
  12. Northern Territory Government 2017, Fishery Status Reports 2015, Fishery Report 118, Northern Territory Government Department of Resources, Darwin, Northern Territory.
  13. Parks Australia 2018, Gulf of Carpentaria Marine Park, Commonwealth of Australia.
  14. Pidd, A, Jacobsen, I, Walton, L and Lawson, A 2021, East Coast Inshore Large Mesh Net Fishery Level 2 Ecological Risk Assessment, Target & Byproduct Species, Technical Report, State of Queensland, Brisbane, Queensland.
  15. Queensland Department of Agriculture and Fisheries 2016. Grey Mackerel Update.
  16. Queensland Department of Agriculture and Fisheries 2022, Harvest Strategies.
  17. Ryan, KL, Lai, EK and Smallwood, CB 2022, Boat-based recreational fishing in Western Australia 2020/21, Fisheries Research Report 327, Department of Primary Industries and Regional Development, Western Australia.
  18. Teixeira, D, Janes, R and Webley, J, 2021, 2019–20 statewide recreational fishing survey - Social and attitudinal results, Department of Agriculture and Fisheries, Queensland
  19. Welch, D, Buckworth, R, Ovenden, J, Newman, S, Broderick, D, Lester, R, Ballagh, A, Stapley, J, Charters, R and Gribble, N 2009, Determination of management units for grey mackerel fisheries in northern Australia, Fisheries Research and Development Corporation project 2005/010, Fishing and Fisheries Research Centre Technical Report 4, Fishing and Fisheries Research Centre, James Cook University, Townsville, Australia.
  20. Welch, D, Newman, S, Buckworth, R, Ovenden, J, Broderick, D, Lester, R, Gribble, N, Ballagh, A, Charters, R, Stapley, J, Street, R, Garrett, R and Begg, G 2015, Integrating different approaches in the definition of biological stocks: A northern Australian multi-jurisdictional fisheries example using grey mackerel Scomberomorus semifasciatus, Marine Policy, 55:73-80.

Downloadable reports

Click the links below to view reports from other years for this fish.