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Blue Swimmer Crab (2020)

Portunus armatus

  • Danielle Johnston (Department of Primary Industries and Regional Development, Western Australia)
  • Arani Chandrapavan (Department of Primary Industries and Regional Development, Western Australia)
  • Lisa Walton (Department of Agriculture and Fisheries, Queensland)
  • Crystal Beckmann (South Australian Research and Development Institute)
  • Daniel Johnson (Department of Primary Industries, New South Wales)
  • Anna Garland (Department of Agriculture and Fisheries, Queensland)

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Summary

Australia has ten stocks of Blue Swimmer Crab across WA, Qld, NSW and SA. Nine of those stocks are sustainable with one stock in WA classified as depleted.

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Stock Status Overview

Stock status determination
Jurisdiction Stock Stock status Indicators
Queensland North-Eastern Australia Sustainable

Stock assessment, standardised catch rates, fishery-independent recruitment abundance

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Stock Structure

Blue Swimmer Crab is distributed in Australia from the south coast of Western Australia, north to the Northern Territory, across Queensland, down the east coast and to the New South Wales–Victoria border. They are also found in the warmer waters of the South Australian gulfs [Kailola et al. 1993].

In Western Australia, Blue Swimmer Crab is fished in numerous fisheries across five regions. The stock delineation between these regions is unknown [Chaplin et al. 2001; Chaplin et al. 2008]. Stock structure on the east coast of Australia is uncertain, involving overlapping stocks or a semi-continuous stock [Chaplin et al. 2001]. Due to the geographic separation between the major fishing grounds for Blue Swimmer Crab in New South Wales and Queensland, they are managed as two separate biological stocks. In South Australia, research has identified three separate biological stocks of Blue Swimmer Crab—in Spencer Gulf, Gulf St Vincent and on the coastline west of the Eyre Peninsula [Bryars and Adams 1999, Dixon and Hooper 2011].

Here, assessment of stock status is presented at the biological stock level—North-Eastern Australia (Queensland), South-Eastern Australia (New South Wales), Spencer Gulf, Gulf St Vincent and West coast (South Australia), and at the management unit level—Shark Bay, Cockburn Sound, Peel-Harvey Estuary, Western Australian North Coast and Western Australian South-West Coast (Western Australia).

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Stock Status

North-Eastern Australia

The Queensland Blue Swimmer Crab fishery primarily operates in southern Queensland. Prior to 1998, the majority of fishing was conducted inshore, in and around Moreton Bay. In 1998 commercial pot fishers began exploiting Blue Swimmer Crab populations further offshore, in areas that were previously lightly fished. Fishing in offshore waters peaked in 2003, when the offshore harvest contributed approximately 70 per cent to total harvest. By 2015, the offshore harvest had decreased and returned to levels slightly higher than those pre-expansion. This rise and subsequent fall of harvest in the offshore area may indicate a decline in fishable biomass for the offshore area and the biological stock as a whole [Johnston et al. 2018]. However, proposed management reforms and subsequent over-reporting within the fishery prior to the investment warning released in 2003 likely reduced the reporting reliability of commercial catch records around this time [QDAF 2019]. 

Queensland assessed the north-eastern Australian Blue Swimmer Crab stock in 2020 (including data up until the 2018–19 financial year) using an integrated stock assessment model. The model estimated exploitable biomass to be at around 33 per cent relative to unfished levels [Lovett et al. 2020]. Under the current management arrangements (i.e. minimum legal size, no-take females), maximum sustainable yield (MSY) is estimated to be around 722 t [Lovett et al. 2020]. Average combined commercial and recreational harvest from the most recent five years was approximately 394 t (336 and 28 t respectively), well below estimated MSY [Lovett et al. 2020].

Catch rates have been declining since 2003 with the 2018–19 season having recorded the lowest catch rate over the last two decades (17 kg/day). While catch rates in recent years have been low, historical records indicate periods where catch rates have been close to this figure (18 to 22 kg/day between the 1991–92 and 1997–98 fishing seasons). Declining catch rates may indicate a reduction in the level of biomass for the Queensland east coast biological stock. Fishery independent surveys show that recruitment abundance has generally been stable through time, with three distinct peaks in 2008, 2014, and 2017 [Bessell-Browne et. al. 2020], although recruitment target reference points are yet to be established by Fisheries Queensland. The most recent stock assessment [Lovett et al. 2020] estimates that spawning biomass displays similar trends to the exploitable biomass, and in 2018–19 was estimated to be around 60 per cent of 1988–89 levels. This stock is not considered to be recruitment impaired.

Active commercial pot fishing licences and fishing effort (in days fished) decreased between 2003 and 2019 by approximately 70 and 74 per cent respectively [QFISH 2020]. Long term trends in total catch and effort are directly proportional to the expansion and subsequent contraction of fishing in offshore areas [Sumpton et al. 2015], with overall fishing pressure on the Blue Swimmer Crab stock showing a decline.

Spatial closures within the Moreton Bay, Great Sandy Strait and Great Barrier Reef Marine Parks provide some additional protection of the Blue Swimmer Crab biomass from fishing mortality [Johnstone et al. 2018]. Management arrangements in Queensland prohibit the take of female crabs, and a minimum legal size of 115 millimeters carapace width ensures that a high proportion of male Blue Swimmer Crabs have an opportunity to mate before recruitment into the fishery [Johnston et al. 2018]. 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-Eastern Australia (Queensland) biological stock is classified as a sustainable stock.

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Biology

Blue Swimmer Crab Biology [de Lestang et al. 2003a,b, Sumpton et al. 2003]

Biology
Species Longevity / Maximum Size Maturity (50 per cent)
Blue Swimmer Crab 3–4 years, ~ 200 mm CW Varies among locations, 6–14 months, 86–110 mm CW 
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Distributions

Blue Swimmer Crab Spatial Distribution

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Tables

Fishing methods
Queensland
Commercial
Blue Swimmer Crab Trap
Trawl
Indigenous
Various
Recreational
Traps and Pots
Management methods
Method Queensland
Charter
Gear restrictions
Protection of female crabs
Size limit
Spatial closures
Commercial
Effort limits
Gear restrictions
Limited entry
Protection of female crabs
Size limit
Spatial closures
Vessel restrictions
Recreational
Gear restrictions
Possession limit
Protection of female crabs
Size limit
Spatial closures
Catch
Queensland
Commercial 217.25t
Indigenous Unknown
Recreational 28 t (2019–20)

Western Australia – Recreational (catch) Boat-based recreational catch in 2017/18 [Ryan et al. 2019]. Does not include scoop netting and other methods of recreational fishing.

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

New South Wales – Indigenous (Management Methods) https://www.dpi.nsw.gov.au/fishing/aboriginal-fishing

New South Wales – Recreational (Catch)  Recreational catch estimate of 26.7 t is based on (i) an estimated recreational catch of 50 637 Blue Swimmer Crabs by NSW resident recreational anglers in 2013–14 [West et al. 2015]; and (ii) an assumed mean weight of kept Blue Swimmer Crabs of 0.530 kg/crab. This remains the most reliable estimate of annual recreational catch because the 2017-18 survey estimate of 14.2 t  estimated using a mean weight of 0.225 kg/ crab [Murphy et al. 2020] applies only to 1-3 year recreational licence holders.

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Catch Chart

Commercial catch of Blue Swimmer Crab - note confidential catch not shown.

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References

  1. Beckmann, CL, Noell C and Hooper, GE 2020, Blue Crab (Portunus armatus) Fishery 2018/19. Fishery Assessment Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2007/000729-16. SARDI Research Report Series No. 1058. 45pp.
  2. Bessell-Browne, P, Prosser, A, and Garland, A 2020 Pre-recruit abundance indices for eastern king prawn, blue swimmer crab and snapper in south eastern Queensland. Department of Agriculture and Fisheries. Brisbane, Queensland.
  3. Bryars, S and Adams, M 1999, An allozyme study of the blue swimmer crab, Portunus pelagicus (Crustacea: Portunidae), in Australia: stock delineation in southern Australia and evidence for a cryptic species in northern waters, Marine and Freshwater Research, 50: 15–26.
  4. Chandrapavan A, Caputi N, Kangas M. 2019. The decline and recovery of a crab population from an extreme marine heatwave and a changing climate. Frontiers in Marine Science. 6 (510).
  5. Chandrapavan A, Kangas M, Johnston D, Caputi N, Hesp A, Denham A, Sporer E . 2018. Improving the confidence in the management of the blue swimmer crab (Portunus armatus) in Shark Bay. Part 1: Rebuilding of the Shark Bay Crab Fishery. FRDC Project No. 2012/15. Fisheries Research Report No. 285. Department of Fisheries, Western Australia.
  6. Chaplin, J, Yap, ES, Sezmis, E and Potter, IC 2001, Genetic (microsatellite) determination of the stock structure of the blue swimmer crab in Australia, Fisheries Research and Development report, FRDC project 98/118, Murdoch University, Western Australia.
  7. Chaplin, JA and Sezmis, E 2008, A genetic assessment of the relationships among the assemblages of the blue swimmer crab, Portunus pelagicus, in Cockburn Sound, the Swan River Estuary and Warnbro Sound, Final report to the Department of Fisheries, Western Australia, Centre for Fish and Fisheries Research, Murdoch University.
  8. de Lestang, S, Bellchambers, LM, Caputi, N, Thomson, AW, Pember, MB, Johnston, DJ and Harris, DC 2010, Stock– recruitment–environment relationship in a Portunus pelagicus fishery in Western Australia, in GH Kruse, GL Eckert, RJ Foy, RN Lipcius, B Sainte-Marie, DL Stram and D Woodby (eds), Biology and management of exploited crab populations under climate change, Alaska Sea Grant, University of Alaska, Fairbanks, doi: 10.4027/bmecpcc.2010.06.
  9. de Lestang, S, Hall, NG and Potter, IC 2003a, Reproductive biology of the Blue Swimmer Crab, Portunus pelagicus (Decapoda: Portunidae) in five water bodies on the west coast of Australia, Fishery Bulletin, 101: 745–757.
  10. de Lestang, S, Hall, NG and Potter, IC 2003b, Do the age compositions and growth of the crab Portunus pelagicus in marine embayments and estuaries differ?, Journal of the Marine Biological Association of the United Kingdom, 83: 1– 8.
  11. Dixon, CD and Hooper, GE 2011, Blue Crab (Portunus pelagicus) Fishery 2009/10, Stock assessment report to Primary Industries and Resources South Australia (Fisheries and Aquaculture), South Australian Research and Development Institute publication F2007/000729-7, SARDI research report series 531, SARDI, Adelaide.
  12. DPIRD (2020). Blue Swimmer Crab Resource of Shark Bay Harvest Strategy 2020-2025 Version 1.0. Fisheries Management Paper No 300. Department of Primary Industries and Regional Development, Western Australia.
  13. Haddon, M. Punt, A. and Burch, P 2018, simpleSA: A package containing functions to facilitate relatively simple stock assessments. R package version 0.1.18.
  14. Henry GW, Lyle JM 2003, The national recreational and Indigenous fishing survey. Fisheries Research and Development Corporation, Canberra.
  15. Johnson, D D 2020, Status of Australian Fish Stocks 2020 – NSW Stock status summary – Blue Swimmer Crab (Portunus armatus).
  16. Johnson, DD, Gray, CA and Macbeth, WG 2010, Reproductive biology of Portunus pelagicus in a south-east Australian estuary, Journal of Crustacean Biology, 30: 200–205.
  17. Johnston, D, Chandrapavan, A, Garland, A, Beckmann, C, and Johnson, D (2018) Blue Swimmer Crab (Portunus armatus). Status of Australian fish stock reports 2018. Fisheries Research and Development Corporation, Canberra.
  18. Johnston, D, Chandrapavan, A, Wise, B and Caputi, N 2014, Assessment of blue swimmer crab recruitment and breeding stock levels in the Peel–Harvey Estuary and status of the Mandurah to Bunbury Developing Crab Fishery, Fisheries research report 258, Western Australian Department of Fisheries, Perth.
  19. Johnston, D, Harris, D, Caputi, N, de Lestang, S and Thomson, A 2011b, Status of the Cockburn Sound Crab Fishery, Fisheries research report 219, Western Australian Department of Fisheries, Perth.
  20. Johnston, D, Yeoh, D, Harris, D and Fisher, E 2020a. Blue Swimmer Crab (Portunus armatus) Resource in the West Coast Bioregion, Western Australia. Part 1: Peel-Harvey Estuary, Cockburn Sound and Swan-Canning Estuary. Fisheries Research Report No. 307. Department of Primary Industries and Regional Development, Western Australia. 194 pp
  21. Johnston, D, Yeoh, D, Harris, D and Fisher, E 2020b. Blue Swimmer Crab (Portunus armatus) and Mud Crab (Scylla serrata and Scylla olivacea) Resources in the North Coast and Gascoyne Coast Bioregions, Western Australia. Fisheries Research Report No. 306. Department of Primary Industries and Regional Development, Western Australia. 156pp.
  22. Johnston, DJ, Harris, D, Caputi, N and Thomson, P 2011a, Decline of a blue swimmer crab (Portunus pelagicus) fishery in Western Australia—history, contributing factors and future management strategy, Fisheries Research, 109(1): 119– 130.
  23. Johnston, DJ, Smith, KA, Brown, JI, Travaille, KL, Crowe, F, Oliver, RK and Fisher, EA 2015, Western Australian Marine Stewardship Council Report Series No 3: West Coast Estuarine Managed Fishery (Area 2: Peel-Harvey) and Peel-Harvey Estuary Blue Swimmer Crab Recreational Fishery. Department of Fisheries, Western Australia. 284 pp.
  24. Kailola, PJ, Williams, MJ, Stewart, PC, Reichelt, RE, McNee, A and Grieve, C 1993, Australian fisheries resources, Bureau of Resources and Fisheries Research and Development Corporation, Canberra.
  25. Kumar, MS, Xiao, Y, Venema, S and Hooper, G 2003, Reproductive cycle of the blue swimmer crab, Portunus pelagicus, off southern Australia, Journal of the Marine Biological Association of the United Kingdom, 83: 983–994.
  26. Lovett, R, O'Neill, MF, and Garland, A 2020 Stock assessment of Queensland east coast blue swimmer crab (Portunus armatus). Department of Agriculture and Fisheries. Brisbane, Queensland.
  27. Martell, S and Froese, R 2013, A simple method for estimating MSY from catch and resilience. Fish and Fisheries 14: 504-514.
  28. Murphy, JJ, Ochwada-Doyle, FA, West, LD, Stark, KE and Hughes, JM, 2020. The NSW Recreational Fisheries Monitoring Program - survey of recreational fishing, 2017/18. NSW DPI - Fisheries Final Report Series No. 158.
  29. PIRSA (2013) Management Plan for the South Australian commercial Marine Scalefish Fishery. The South Australian Fisheries Management Series, Paper number 59. 141pp
  30. PIRSA 2020 Management Plan for the South Australian Commercial Blue Crab Fishery. South Australian Fisheries Management Series Paper No. 75. Adelaide, Australia: Primary Industries and Regions South Australia (Fisheries and Aquaculture).
  31. QFish, Department of Agriculture and Fisheries, www.qfish.gov.au
  32. Queensland Department of Agriculture and Fisheries 2019 Mud and blue swimmer crab (C1) fishery scoping study. Technical report. Brisbane, Queensland.
  33. Ryan KL, Hall NG, Lai EK, Smallwood CB, Tate A, Taylor SM, Wise BS 2019. Statewide survey of boat-based recreational fishing in Western Australia 2017/18. Fisheries Research Report No. 297, Department of Primary Industries and Regional Development, Western Australia.
  34. Steer MA, Fowler AJ, Rogers PJ, Bailleul F, Earl J, Matthews D, Drew M and Tsolos A. (2020). Assessment of the South Australian Marine Scalefish Fishery in 2018 (PDF 8.7 MB). South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2017/000427-3. SARDI Research Report Series No. 1049.
  35. 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.
  36. Sumpton, W, Campbell, M, O’Neill, M, McLennan, M, Campbell A and Leigh, G 2015, Assessment of the blue swimmer crab (Portunus armatus) fishery in Queensland. Department of Agriculture and Fisheries, Brisbane.
  37. Sumpton, W, Gaddes, S, McLennan, M, Campbell, M, Tonks, M, Good, N and Hagedoorn, W 2003, Fisheries biology and assessment of the blue swimmer crab (Portunus pelagicus) in Queensland, Queensland Department of Primary Industries and Fisheries Research and Development Corporation project 98/117.
  38. West, LD, Stark, KE, Murphy, JJ, Lyle, JM and Ochwada-Doyle, FA 2015, Survey of recreational fishing in New South Wales and the ACT, 2013/14. Fisheries Final Report Series No. 149. NSW Department of Primary Industries, Wollongong.

Downloadable reports

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