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Blue Swimmer Crab (2018)

Portunus armatus

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

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Summary

Australia has ten stocks of Blue Swimmer Crab across WA, Qld, NSW and SA. Eight of those stocks are sustainable with two stocks in WA classified as recovering.

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Stock Status Overview

Stock status determination
Jurisdiction Stock Fisheries Stock status Indicators
South Australia Gulf St. Vincent BCF, MSF Sustainable Fishery-independent legal-sized relative catch rate
South Australia Spencer Gulf BCF, MSF Sustainable Fishery-independent legal-sized relative catch rate
South Australia West Coast MSF Sustainable Catch, CPUE
BCF
Blue Crab Fishery (SA)
MSF
Marine Scalefish Fishery (SA)
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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. 1983].

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

Gulf St. Vincent

The process for determining the status of the Gulf St. Vincent biological stock is the same as for the Spencer Gulf stock, using a similar fishery-independent pot survey design, and the same definition and usage of limit reference points based on survey catch rate, as an index of relative biomass and fishing mortality [PIRSA, 2018]. The most recent stock assessment by Beckmann and Hooper (2018) reported that, during the 2016–17 season (1 July 2016–30 June 2017), the TACC was fully harvested (245 t) for the third consecutive year.

Catch rates of legal-sized crabs in 2017 (2.8 kg crabs per pot-lift) were above the target reference point (1.2 kg crabs per pot-lift) and the second highest on record [Beckmann and Hooper 2018]. The catch rate of legal-sized crabs has been above the target reference point during each of the last three surveys. The above evidence indicates that the biomass of this stock is unlikely to be depleted, that recruitment is unlikely to be impaired and that 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 Gulf St. Vincent (South Australia) biological stock is classified as a sustainable stock.

Spencer Gulf

In the South Australian gulfs, access to take Blue Swimmer Crabs is provided via a Blue Crab Fishery (BCF) or a Marine Scalefish Fishery (MSF) licence endorsed with quota entitlements. MSF licence holders predominantly use hoop and drop nets while, the pot fishing sector of the BCF uses specifically designed crab pots. TACC levels have been set since 1996 to limit Blue Swimmer Crab catches within ecologically sustainable limits. Since 1999–2000, exploitation rates have been limited by setting the TACC at a level below the maximum historical catch for the fishery. The TACC during the 2016/17 season (1 July 2016–30 June 2017) was 382 t and was fully harvested. Throughout South Australia, a LMS of 110 mm CW is enforced, at which size crabs are approximately 14–18 months old and sexually mature. Females produce at least two batches of eggs each season [Kumar et al. 2003].

The most recent stock assessment report [Beckmann and Hooper 2018] used data up to 30 June 2017. The primary measures of biomass and fishing mortality for the Spencer Gulf biological stock are the relative abundance of legal-sized crabs, obtained from catch rates in fishery-independent pot surveys. The catch rates of legal-sized crabs from fishery-independent surveys are considered to be a more reliable index for biomass and fishing mortality than fishery-dependent data because the fishery-independent sampling design has remained relatively consistent since 2002. Survey catch rates are compared with limit reference points defined in the South Australian Blue Crab Fishery Management Plan [PIRSA 2018]. These reference points were set at the lower end of the observed range of relative catch rates in the reference period 2002–10, to ensure that relative abundance remains within the range of historical values during a period when the TACC was constant and considered to be harvested sustainably.

Catch rates of legal-sized crabs in 2017 (3.1 kg crabs per pot-lift) were above the target reference point (2.7 kg crabs per pot-lift) and the highest on record [Beckmann and Hooper 2018]. The catch rate of legal-sized crabs has been above the target reference point during five of the last seven surveys. The above evidence indicates that the biomass of this stock is unlikely to be depleted, that recruitment is unlikely to be impaired, and that 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 Spencer Gulf (South Australia) biological stock is classified as a sustainable stock.

West Coast

On the West Coast of South Australia, access to take Blue Swimmer Crabs is provided via a MSF licence. MSF licence holders predominantly use hoop and drop nets. Fishers in this fishery target a range of species, and effort patterns generally reflect changes in relative seasonal abundance of the various species and their market prices. The West Coast zone is not subject to the quota management system and is managed separately to the BCF. This zone of the fishery operates under the Management Plan for the MSF [PIRSA 2018] that specifies general performance indicators.

The most recent stock assessment by Beckmann and Hooper (2018) reported a total harvest of 47 t during the 2016–17 season (1 July 2016–30 June 2017) and this was above the long-term average (1893/84–2015/16; 27 ± 4 t). The primary indices of biomass and fishing mortality for the West Coast Gulf biological stock are the commercial CPUE and catch trends. Comparison of recent CPUE and catch trends to values in the past decade is considered to provide a reliable proxy for relative biomass and fishing mortality. These historical values have been stable at relatively high levels, indicating that the biomass of this stock was unlikely to be depleted or that recruitment was unlikely to be impaired in the past decade.

The total harvest in 2016–17 was above the long-term average (1983/84–2015/16; 27 ± 4 t). The 2016–17 targeted crab net catch rate was 65 kg per boat day and the catch rate has remained around this level since 2007–08 (range: 62–79 kg per boat day). The above evidence indicates that the biomass of this stock is unlikely to be depleted, that recruitment is unlikely to be impaired and that 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 West Coast (South Australia) 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
South Australia
Commercial
Lift nets
Blue Swimmer Crab Trap
Recreational
Diving
Coastal, Estuary and River Set Nets
Management methods
Method South Australia
Commercial
Gear restrictions
Limited entry
Protection of egg-bearing females
Size limit
Spatial closures
Spatial zoning
Temporal closures
Total allowable catch
Recreational
Bag limits
Boat limits
Gear restrictions
Protection of egg-bearing females
Size limit
Spatial closures
Active vessels
South Australia
3, 4 in BCF, 1, 30 in MSF
BCF
Blue Crab Fishery (SA)
MSF
Marine Scalefish Fishery (SA)
Catch
South Australia
Commercial 630.88t in BCF, 46.95t in MSF
Indigenous Unknown
Recreational 376 t (Dec 2013–Nov 2014)
BCF
Blue Crab Fishery (SA)
MSF
Marine Scalefish Fishery (SA)

Western Australia – Recreational (catch) Boat-based recreational catch from 1 May 2013–30 April 2014 [Ryan et al. 2018].

Queensland – Indigenous (Management Methods) Under the Fisheries Act 1994 (Qld), Indigenous fishers in Queensland are entitled to use prescribed traditional and non-commercial fishing apparatus in waters open to fishing. Size and possession limits, and seasonal closures do not apply to Indigenous fishers. Further exemptions to fishery regulations may be applied for through permits.

New South Wales – Indigenous (Management Methods) (a) Aboriginal Cultural Fishing Interim Access Arrangement—allows an Indigenous 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 for themselves; (b) The Aboriginal cultural fishing authority is the authority that Indigenous persons can apply to take catches outside the recreational limits under the Fisheries Management Act 1994 (NSW), Section 37d) (3)(9), Aboriginal cultural fishing authority; and (c) In cases where the Native Title Act 1993 (Cth) applies, fishing activity can be undertaken by the person holding native title in line with S.211 of that Act, which provides for fishing activities for the purpose of satisfying their personal, domestic or non-commercial communal needs. In managing the resource where native title has been formally recognised, the native title holders are engaged with to ensure their native title rights are respected and inform management of the State's fisheries resources.

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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 and Hooper, GE 2018, Blue Crab (Portunus armatus) Fishery 2016/17. Fishery Assessment Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2007/000729-14. SARDI Research Report Series No. 980. 59pp.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. Henry GW, Lyle JM 2003, The national recreational and Indigenous fishing survey. Fisheries Research and Development Corporation, Canberra.
  10. 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.
  11. 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.
  12. 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.
  13. Johnston, D., Marks, R. and O’Malley, J. (2018). West Coast Blue Swimmer Crab Fishery Status Report 2017, in Gaughan, D.J. and Santoro, K. (eds), Status reports of the fisheries and aquatic resources of Western Australia 2015/16: the state of the fisheries. Report prepared by the Western Australian Department of Fisheries.
  14. 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.
  15. 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.
  16. 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.
  17. 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.
  18. PIRSA 2018, Management Plan for the South Australian Commercial BCF. South Australian Fisheries Management Series Paper No. 75. Adelaide, Australia: Primary Industries and Regions South Australia (Fisheries and Aquaculture).
  19. Queensland Department of Agriculture and Fisheries 2018, Queensland Stock Status Assessment Workshop Proceedings 2018. Species Summaries. 19–20 June 2018, Brisbane.
  20. Ryan, KL, Hall, NG, Lai, EK, Smallwood, CB, Taylor, SM, and Wise, BS 2017, State-wide survey of boat based recreational fishing in Western Australia 2015/16. , Fisheries research report 287, Department of Primary Industries and Regional Development, western Australia, 205pp.
  21. 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.
  22. 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.
  23. 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.
  24. West, LD, Stark, KE, Murphy, JJ, Lyle, JM and Ochwada-Doyle, FA 2016, Survey of Recreational Fishing in New South Wales and the ACT, 2013/14, NSW Fisheries Final Report Series 149.

Archived reports

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