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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
Queensland North-Eastern Australia BSCF, ECOTF Sustainable Estimated biomass, standardised catch rates, fishery- independent recruitment abundance
BSCF
Blue Swimmer Crab Fishery (QLD)
ECOTF
East Coast Otter Trawl Fishery (QLD)
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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

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 is of concern, and may indicate a decline in fishable biomass for the offshore area and the biological stock as a whole [QDAF 2018].

Queensland assessed the north-eastern Australian Blue Swimmer Crab stock in 2015 (including data up until 2014) using an integrated stock assessment. Representative outputs for Moreton Bay and Sunshine Coast were used to determine status for the entire biological stock [Sumpton et al. 2015]. The model estimated spawning biomass between 38 and 58 per cent of assumed equilibrium [Sumpton et al. 2015]. At the current minimum legal size (MLS), median maximum sustainable yield (MSY) estimates range from 375 to 750 t [Sumpton et al. 2015]. Current combined commercial and recreational harvest from the representative area of approximately 368 t (336 and 32 t respectively) is below this range [QDAF 2018].

Standardised catch rates in Moreton Bay and Sunshine Coast have been relatively stable in recent years although at lower levels than historically (76 and 71 per cent of the 1989 to 2016 average respectively), this may indicate a reduction in the level of biomass in these areas. Catch rates in Hervey Bay have declined significantly in recent years but are still above half of the historical average (62 per cent of the 1989 to 2016 average) [QDAF 2018]. Fishery independent recruitment surveys show a relative increase in recruitment in the inshore area since 2009 (QDAF 2018], although recruitment target reference points are yet to be established by Fisheries Queensland. The most recent assessment [Sumpton et al. 2015] estimates that spawning biomass in 2014 was between 38 and 58 per cent of 1989 levels. This stock is not considered to be recruitment impaired.

The recent stock assessment also estimated fishing pressure on the exploitable component of the stock. Analyses indicated male legal Blue Swimmer Crab abundance to be between 22 and 42 per cent of assumed equilibrium [Sumpton et al. 2015]. Active commercial pot fishing licences and fishing effort (in days fished) decreased between 2003 and 2017 by approximately 50 per cent [QDAF 2018]. 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 protection of the Blue Swimmer Crab biomass from fishing mortality [QDAF 2018]. Management arrangements in Queensland prohibit the take of female crabs, and a minimum legal size ensures that a high proportion of male Blue Swimmer Crabs have an opportunity to mate before recruitment into the fishery [QDAF 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
Otter Trawl
Traps and Pots
Indigenous
Traditional apparatus
Recreational
Traps and Pots
Management methods
Method Queensland
Charter
Gear restrictions
Protection of female crabs
Size limit
Spatial closures
Commercial
Catch limits
Gear restrictions
Limited entry
Protection of female crabs
Size limit
Spatial closures
Vessel restrictions
Recreational
Gear restrictions
Protection of female crabs
Size limit
Spatial closures
Active vessels
Queensland
104 in BSCF, 212 in ECOTF
BSCF
Blue Swimmer Crab Fishery (QLD)
ECOTF
East Coast Otter Trawl Fishery (QLD)
Catch
Queensland
Commercial 322.00kg in BSCF, 473.41t in BSCF
Indigenous Unknown
Recreational 36 t (2013–14)
BSCF
Blue Swimmer Crab Fishery (QLD)

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.