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Grey Mackerel (2020)

Scomberomorus semifasciatus

  • Anthony Roelofs (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 Government)

Date Published: June 2021

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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
Queensland North East Queensland Sustainable

Quantitative stock assessment, biomass, fishing mortality, catch, effort

Queensland South East Queensland Sustainable Quantitative stock assessment, biomass, fishing mortality, catch, effort
Queensland Gulf of Carpentaria Sustainable

Biomass, fishing mortality, catch, catch rate

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Stock Structure

Grey Mackerel (Scomberomorous semifasciatus) are found in southern Papua New Guinea and northern Australia from Shark Bay, Western Australia, to northern New South Wales. There are at least five Grey Mackerel biological stocks across northern Australia, with a possible additional stock 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].

Here, assessment of stock status is presented at the biological stock level—Western Australia, North West Northern Territory, Gulf of Carpentaria, 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. Queensland and the Northern Territory share management of the Gulf of Carpentaria biological stock through the Queensland Fisheries Joint Authority. Queensland took the majority (91 per cent; 741 tonnes (t)) of the commercial harvest in 2019. Queensland introduced changes to the net fishery at the commencement of the 2012 season to reduce pressure on Grey Mackerel. These measures decreased the total length of available net by two-thirds, from 27 km to 9 km in the offshore component of the fishery. Changes made for the Queensland inshore fishery (within seven nautical miles of the coast) also reduced the capacity for boats to target Grey Mackerel. Commercial effort in 2019 (1 013 days fished) in Queensland was below the 10-year average (1 102 days fished from 2009 to 2018) [QFISH 2020]. Grey Mackerel in the Northern Territory are primarily taken in the NT Offshore Net and Line Fishery (ONLF). In 2018 the ONLF transitioned to an individual transferable quota management system, which restricts harvests of Grey Mackerel within a species-specific total allowable catch limit. 

Stock reduction analysis of Grey Mackerel in the Gulf of Carpentaria, using Queensland and Northern Territory catches, estimated that the biomass in 2019 was 55 per cent of the unfished biomass and that the harvest rate was at 57 per cent of that required to achieve MSY [Northern Territory Government, unpublished]. The above evidence indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. The level of fishing mortality is also unlikely to cause the stock to become recruitment impaired.

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

North East Queensland

The North East Queensland biological stock is managed as part of a Queensland east coast-wide fishery. Grey Mackerel is primarily a commercial gillnet-caught species [Bessell-Browne et al. 2019] with an annual average of two per cent of catches taken by line fishing since 2005. The most recent stock assessment (using 2018 data) did not detect any trend in Grey Mackerel abundance that might indicate overfishing at the east coast-wide level or evidence to advocate against the current fishery-wide TACC of 250 t although it did suggest a slightly lower equilibrium MSY for the east coast at 227 t [Bessell-Browne et al. 2019]. The assessment suggests that the north east stock is currently at 48 per cent (range 37–58 per cent) of unfished biomass. Current harvest levels (39 t) [QFISH 2020] are below the equilibrium MSY level and the longer-term target of 60 per cent of unfished biomass for each stock. The above evidence indicates that the biomass of this stock is unlikely to be recruitment depleted and that recruitment is unlikely to be impaired.

Fishing pressure on the north east stock has been low in recent years, following the introduction of the current fishery-wide financial year TACC of 250 t. Prior to the introduction of the TACC, nominal fishing effort (days when Grey Mackerel were caught) in the north east averaged 1 020 annual net fishing days between 2004–05 and 2008–09, after which it decreased to an average of 516 annual net fishing days between 2009–10 and 2018–19. This level of fishing mortality is unlikely to cause the stock to become recruitment impaired.

On the basis of the evidence provided above, the North East Queensland biological stock is classified as a sustainable stock.

South East Queensland

The South East Queensland biological stock is managed as part of a Queensland east coast-wide fishery. Grey Mackerel is primarily a commercial gillnet-caught species [Bessell-Browne et al. 2019] with an annual average of two per cent of catches taken by line fishing since 2005. The most recent stock assessment (using 2018 data) did not detect any trend in east coast Grey Mackerel abundance that might indicate overfishing at the east coast-wide level or evidence to advocate against the current fishery-wide TACC of 250 t although it did recommend the equilibrium MSY for the east coast to be slightly lower at 227 t [Bessell-Browne et al. 2019]. The assessment suggests that the south east stock is currently at 51 per cent (range 40–61 per cent) of unfished biomass. Current harvest levels (59 t) [QFISH 2020] are below the equilibrium MSY level and the longer term target of 60 per cent of unfished biomass for each stock. The above evidence indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired.

Fishing pressure on the South East Queensland stock has remained low following the introduction of the current fishery-wide financial year TACC of 250 t. Prior to the introduction of the TACC, nominal fishing effort (days when Grey Mackerel were caught) in the south east averaged 1 427 annual net fishing days between 2004–05 and 2008–09, after which it decreased to an average of 792 annual net fishing days between 2009–10 and 2018–19. This level of fishing mortality is unlikely to cause the stock to become recruitment impaired.

On the basis of the evidence provided above, the South East Queensland biological stock is classified as a sustainable stock.

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Biology

Grey Mackerel biology [Cameron and Begg 2002, Department of Agriculture and Fisheries 2016]

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
Queensland
Commercial
Line
Net
Recreational
Spearfishing
Hook and Line
Indigenous
Various
Management methods
Method Queensland
Charter
Gear restrictions
Marine park closures
Possession limit
Size limit
Spatial zoning
Commercial
Fishery spatial closures
Gear restrictions
Limited entry
Marine park closures
Size limit
Spatial zoning
Total allowable catch
Vessel restrictions
Recreational
Gear restrictions
Marine park closures
Possession limit
Size limit
Spatial zoning
Catch
Queensland
Commercial 838.15t
Charter Unknown
Indigenous Unknown
Recreational Unknown

Western Australian – Recreational (catch) Western Australian boat-based recreational catch survey from 1 Sep 2017–30 Aug 2018 [Ryan et al 2019]. 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 “…without derogating from any other law in force in the Territory, nothing in a provision of this Act or an instrument of a judicial or administrative character made under it limits the right of Aboriginals who have traditionally used the resources of an area of land or water in a traditional manner from continuing 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

Indigenous The reporting period for the Commonwealth (Torres Strait) is the 2012–13 financial year.

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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. Department of Agriculture and Fisheries 2016. Grey Mackerel Update.
  6. Gaughan, DJ and Santoro, K (eds) 2018, Status Reports of the Fisheries and Aquatic Resources of Western Australia 2016/17: The State of the Fisheries. Department of Primary Industries and Regional Development, Western Australia.
  7. Great Barrier Reef Marine Park Authority, 2011, A vulnerability assessment for the Great Barrier Reef - Grey mackerel.
  8. 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.
  9. Northern Territory Government 2012, Fishery Status Reports 2011, Fishery Report 111, Northern Territory Government.
  10. Northern Territory Government 2017, Fishery Status Reports 2015, Fishery Report 118, Northern Territory Government Department of Resources, Darwin, Northern Territory.
  11. QFish, Department of Agriculture and Fisheries, www.qfish.gov.au
  12. Ryan, KL, Hall, NG, Lai, EK, Smallwood, CB, Tate, A, Taylor, SM and Wise BS 2019, State-wide survey of boat-based recreational fishing in Western Australia 2017/18, Fisheries Research Report 297, Department of Primary Industries and Regional Development, Western Australia.
  13. Welch, D, Buckworth, R, Ovenden, J, Newman, S, Broderick, D, Lester, R, Ballagh, A, Stapley, J, Charters, R and GribbleN 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.
  14. 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

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