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Spotted Mackerel

Scomberomorus munroi

  • Lenore Litherland (Department of Agriculture and Fisheries, Queensland)
  • Grant Johnson (Department of Primary Industry and Resources, Northern Territory)
  • John Stewart (Department of Primary Industries, New South Wales)
  • Paul Lewis (Department of Fisheries, Western Australia)

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Stock Status Overview

Stock status determination
Jurisdiction Stock Fisheries Stock status Indicators
New South Wales Eastern Australia OTLF Sustainable Biomass, catch and catch rate, fishery-dependent length and age frequency, estimates of total mortality rate
OTLF
Ocean Trap and Line (NSW)
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Stock Structure

Spotted Mackerel occurs in continental shelf waters along Australia's western and northern coast and along the eastern coast, to central New South Wales1,2. In northern and western Australian waters the delineation of stocks is not clear. Results from an otolith microchemistry study indicate that fish from Gove and Joseph Bonaparte Gulf may belong to separate stocks2. Therefore, a Northern Australian biological stock and a Western Australian biological stock are assumed here. In Eastern Australian waters, Spotted Mackerel comprise a single stock (confirmed through genetic analysis, otolith microchemistry and tagging studies) that is genetically isolated from fish in the northern Arafura Sea1,2.

Here, assessment of stock status is presented at the biological stock level—Western Australia, Northern Australia and Eastern Australia.

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Stock Status

Eastern Australia

Spotted Mackerel is commonly fished throughout its distribution along the east coast of Australia. Queensland and New South Wales both access the part of the biological stock that occurs in their waters. Most of the fishery occurs in Queensland waters, with a smaller seasonal fishery in northern New South Wales waters9 during late-summer–autumn. An assessment of this stock conducted in 2005 indicated that catches in 2002 were near, or above, the estimated maximum sustainable yield (MSY) and that the stock was at risk of being overfished7. Management measures introduced in Queensland since 2002 have substantially reduced that risk4. These measures included a limit on the commercial harvest, the prevention of fishing using ring nets, by-product possession limits for net fishers and a reduced recreational possession limit. As a result of these restrictions, the Queensland commercial net harvest has been stable, but low. In 2014–15, the Queensland commercial line harvest was 72 t, which is above the 10-year average of 60 t, but below the annual commercial catch limit of 140 t4,5,10. The number of active licences and days fished in 2014–15 was below the 10-year average4. The Queensland recreational harvest of Spotted Mackerel decreased between 2001 and 2013–145, reflecting in part the reduction in recreational line fishing effort between 2001 and 201111. The NSW recreational harvest of Spotted Mackerel was similar during 2001 and 2013–14 at between 10 000 and 13 000 fish, estimated to weigh around 41 t9,10. In 2014–15, the best estimate of the combined harvest of the Eastern Australian biological stock is below the estimated MSY of 296 t4,5,10. As the most recent stock assessment was completed 10 years ago (using data up to 2002) and alternative indicators have been developed, a weight-of-evidence approach was used to determine the status of this biological stock.

 

Nominal catch per unit effort for the Queensland commercial line harvest has been higher than historic levels for the past 3 years4. Nominal catch rates in New South Wales have fluctuated, but show no overall trends over the past 20 years9. The minimum legal size in Queensland and New South Wales is set above the size at maturity for males and equal to the size at maturity for females, providing some protection of the spawning stock6,8. In Queensland, fishery-dependent monitoring of the recreational and commercial harvest shows relatively consistent length structures during the past 9 years4. Fishery-dependent monitoring indicates a range of ages, including older fish (4–7 year olds) are present in the harvest, with 2–5 year olds dominating the catch4. Estimates of total mortality rate, derived from the fishery-dependent age composition data, indicate fishing mortality was lower than natural mortality between 2007–08 and 2014–154. These are positive indicators of a stable spawning biomass with continuing recruitment. The above evidence indicates that the biomass of the Eastern Australian biological stock is unlikely to be recruitment overfished and the current level of fishing pressure is unlikely to cause the Eastern Australian biological stock to become recruitment overfished.

 

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

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Biology

Spotted Mackerel biology1,2,4,7

Biology
Species Longevity / Maximum Size Maturity (50 per cent)
Spotted Mackerel 8 years; 1 230 mm  TL  Females: 1–2 years; 600 mm  TL Males: 1–2 years; 520 mm  TL
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Distributions

Distribution of reported commercial catch of Spotted Mackerel

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Tables

Fishing methods
New South Wales
Commercial
Hand Line, Hand Reel or Powered Reels
Pelagic Longline
Trolling
Recreational
Spearfishing
Hand Line, Hand Reel or Powered Reels
Indigenous
Hand Line, Hand Reel or Powered Reels
Management methods
Method New South Wales
Commercial
Fishery spatial closures
Gear restrictions
Limited entry
Marine park closures
Size limit
Spatial zoning
Vessel restrictions
Indigenous
Bag limits
Gear restrictions
Seasonal or spatial closures
Section 31 (1)(c1), Aboriginal cultural fishing authority
Size limit
Recreational
Gear restrictions
Licence
Marine park closures
Possession limit
Size limit
Active vessels
New South Wales
57 in OTLF
OTLF
Ocean Trap and Line (NSW)
Catch
New South Wales
Commercial 16.33t in OTLF
Indigenous Unknown
Recreational 41 t (2013–14)
OTLF
Ocean Trap and Line (NSW)

a Queensland - Indigenous In Queensland, under the Fisheries Act 1994, Indigenous fishers are able to use prescribed traditional and non-commercial fishing apparatus in waters open to fishing. Size and bag limits and seasonal closures do not apply to Indigenous fishers. Further exemptions to fishery regulations can be obtained through permits
b New South Wales - Indigenous Aboriginal Cultural Fishing Interim Access Arrangement allows an Aboriginal fisher in New South Wales to take in excess of a recreational bag limit in certain circumstances, for example, if they are doing so to provide fish to other community members who cannot harvest themselves.
c New South Wales - Indigenous Aboriginal cultural fishing authority - the authority that indigenous persons can apply for to take catches outside the recreational limits under the Fisheries Management Act 1994 (NSW), Section 37 (1)(c1), Aboriginal cultural fishing authority. 

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Catch Chart

Commercial catch of Spotted Mackerel

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Effects of fishing on the marine environment

  • The majority of fishing for Spotted Mackerel uses trolled lines. This method has almost no impact on the habitats where it is used. Commercial coastal gillnets used in Queensland waters have minimal impact on the environment and are quite selective in their harvest12. In general, gillnet methods used by commercial fishers in nearshore waters result in minimal bycatch relative to the harvest of the target species. Mesh size regulations help to ensure that target species caught by these methods are within an appropriate size range. Commercial coastal gillnets are not used in New South Wales waters.
  • Line-based fishing methods in nearshore waters can result in the capture and release of non-target species and undersized fish5,10. The rates of survival for released line caught Spotted Mackerel are unquantified and discard mortality could be substantial.
  • Discarded fishing tackle from fishers poses a risk to seabirds and marine life, which can become entangled in or injured by discarded gear13. Programs to safely dispose of unwanted fishing tackle are in place in south-east Queensland and New South Wales13.
  • Commercial gillnets can occasionally interact with threatened, endangered and protected species. The impact on populations of these species is unquantified. In most jurisdictions, commercial fishers are required to report all interactions with protected species.
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Environmental effects on Spotted Mackerel

  • Juvenile Spotted Mackerel are dependent on nearshore waters for survival and may be sensitive to declines in water quality resulting from land based influences14
  • Spotted Mackerel prey on schooling baitfish. Climate change impacts on baitfish in Queensland waters are poorly understood14.
  • Changes in coastal currents and water temperatures associated with climate change have the potential to alter fish behaviour (for example, spawning activity and migration) and to affect the dispersal of eggs and larvae, which may influence the subsequent recruitment of Spotted Mackerel into fisheries14–16.
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References

  1. 1 Begg, G, Keenan, C and Sellin, M 1998, Genetic variation and stock structure of school mackerel and spotted mackerel in northern Australian waters, Journal of Fish Biology, 53, 543-559.
  2. 2 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.
  3. 3 West, LD, Lyle, JM, Matthews, SR, Stark, KE and Steffe, AS 2012, Survey of Recreational Fishing in the   Northern Territory, 2009­10, Fishery Report 109, Department of Primary Industry and Fisheries, Darwin.
  4. 4 Department of Agriculture, Fisheries and Forestry 2016, Queensland Stock Status Assessment Workshop 2016, 14-15 June 2016, Brisbane, Australia, Queensland Department of Agriculture and Fisheries.
  5. 5 Webley, J, McInnes, K, Teixeira, D, Lawson, A and Quinn, R 2015, Statewide Recreational Fishing Survey 2013-14. Department of Agriculture and Fisheries, Queensland.Webley, J, McInnes, K, Teixeira, D, Lawson, A and Quinn, R 2015, Statewide Recreational Fishing Survey 2013-14. Department of Agriculture and Fisheries, Queensland.
  6. 6 Begg, GA 1998, 'Reproductive biology of school mackerel (Scomberomorus queenslandicus) and spotted mackerel (S. munroi) in Queensland east-coast waters', Marine and Freshwater Research, vol. 49, no. 3, pp. 261-270.
  7. 7 Begg, GA, O'Neill, MF, Cadrin, SX and Bergenius, MAJ 2005, Stock Assessment of the Australian East Coast Spotted Mackerel Fishery, CRC Reef Research Centre, Townsville.
  8. 8 Begg, GA and Sellin, MJ 1998, 'Age and growth of school mackerel (Scomberomorus queenslandicus) and spotted mackerel (S. munroi) in Queensland east-coast waters with implications for stock structure', Marine and Freshwater Research, vol. 49, no. 2, pp. 109-120.
  9. 9 Stewart, J, Hegarty, A, Young, C, Fowler, AM and Craig, J 2015, Status of Fisheries Resources in NSW 2013-14, NSW Department of Primary Industries, Mosman: 391pp.
  10. 10 West, L.D, Stark, KE, Murphy, JJ, Lyle JM and Doyle, FA 2015, Survey of recreational fishing in New South Wales and the ACT, 2013/14. Fisheries Final Report Series.
  11. 11 Taylor, S, Webley, J and McInnes, K 2012, 2010 statewide recreational fishing survey, Department of Agriculture, Fisheries and Forestry, Brisbane, Australia.
  12. 12 Halliday, IA, Ley, JA, Tobin, A, Garrett, R, Gribble, NA, and Mayer, DG 2001, The effects of net fishing: addressing biodiversity and bycatch issues in Queensland inshore waters (FRDC Project no. 97/206), Department of Primary Industries, Queensland.
  13. 13 Campbell, M 2013, Tactical Research Fund: Reducing the impact of discarded recreational fishing tackle on coastal seabirds. FRDC Project No 2011/057, Queensland Department of Agriculture, Fisheries and Forestry, Brisbane.
  14. 14 Welch, D, Robins, J, Saunders, T, Courtney, A, Harry, A, Lawson, E, Moore, B, Tobin, A, Turnbull, C, Vance, D, and Williams, A 2014, 'Part 2: Species profiles', in D Welch, J Robins and T Saunders (eds.), Implications of climate change impacts on fisheries resources of northern Australia. FRDC Project No: 2010/565, James Cook University, Townsville.
  15. 15 Hobday, AJ, Poloczanska, ES, and Matear, RJ (eds.), 2008, Implications of climate change for Australian fisheries and aquaculture: a preliminary assessment, report to the Australian Government Department of Climate Change, Canberra.
  16. 16 Pearce, A, Lenanton, R, Jackson, G, Moore, J, Feng, M, and Gaughan, D 2011, The “marine heat wave” off Western Australia during the summer of 2010/11, Fisheries Research Report No. 222, Department of Fisheries, Western Australia.