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Blue Swimmer Crab (2023)

Portunus armatus

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

Date Published: June 2023

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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 one stock in WA classified as depleted and one stock In South Eastern Australia classified as depleting.

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Stock Status Overview

Stock status determination
Jurisdiction Stock Stock status Indicators
South Australia Gulf St. Vincent Sustainable Fishery-independent legal-sized relative catch rate
South Australia Spencer Gulf Sustainable Fishery-independent legal-sized relative catch rate
South Australia West Coast Sustainable Catch, CPUE
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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]. Using a high-resolution oceanographic model coupled with a Lagrangian particle tracking framework to simulate larval dispersal, Hewitt et al. 2022 suggest populations of Blue Swimmer Crab in NSW and Queensland appear to constitute demographically separate stocks, supporting the current assessment and management at the state level. 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

IIn 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. The MSF licence holders predominantly use hoop and drop nets while the pot fishing sector of the BCF uses specifically designed crab pots. Determination of stock status is based on a fishery-independent pot survey with trigger and limit reference points based on survey catch rate, as indices of relative biomass and fishing mortality [PIRSA 2020]. The TACC levels have been set since 1996 to limit Blue Swimmer Crab catches within ecologically sustainable limits set in the management plans [PIRSA 2020]. Since 1999–2000, exploitation rates have been limited by setting the TACC at levels below the maximum historical catch for the fishery. Throughout South Australia, a legal minimum size (LMS) of 110 mm carapace width (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 reported that 195.1 t was harvested, which represented 72% of the TACC (269.66 t) in the 2021–22 season [Beckmann and Hooper 2023]. In 2022, legal sized fishery independent survey CPUE was 5.4 kg crabs per pot-lift, which was above the trigger (1.7 kg crabs per pot-lift) and target (2.5 kg crabs per pot-lift) reference points [Beckmann and Hooper 2023]. The above evidence indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. Furthermore, the above evidence indicates 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 biological stock is classified as a sustainable stock.

Spencer Gulf

In the South Australian gulfs, access to commercially harvest Blue Swimmer Crabs is provided via a Blue Crab Fishery (BCF) or a Marine Scalefish Fishery (MSF) licence endorsed with quota entitlements. The MSF licence holders predominantly use hoop and drop nets while, the pot fishing sector of the BCF uses specifically designed crab pots. Determination of stock status is based on a fishery-independent pot survey with trigger and limit reference points based on survey catch rate, as an index of relative biomass and fishing mortality [PIRSA 2020]. The TACC levels have been set since 1996 to limit Blue Swimmer Crab catches within ecologically sustainable limits set in the management plans [PIRSA 2020]. Since 1999–2000, exploitation rates have been limited by setting the TACC at levels below the maximum historical catch for the fishery. Throughout South Australia, a legal minimum size (LMS) of 110 mm carapace width (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 reported that 326.3 t was harvested, which represented 86% of the TACC (381.67 t) for the 2021–22 season [Beckmann and Hooper 2023]. In 2022, legal sized fishery independent survey CPUE was 4.1 kg crabs per pot-lift, which was above the trigger reference point (2.4 kg crabs per pot-lift) [Beckmann and Hooper 2023]. The above evidence indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. Furthermore, the above evidence indicates 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 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 Marine Scalefish Fishery (MSF) licence. MSF licence holders predominantly use hoop and drop nets. 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 assessed in Smart et al. [2023].

Catches continued to decline during 2000s and early 2010s, dropping to a low of 31.2 t in 2016, and have since increased to 58 t in 2021–22 [Smart et al 2023]. The primary indices of biomass and fishing mortality for the West Coast 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 targeted effort was 1,059 fisher days in 2021–22 which produced a CPUE (targeted crab net effort) by fisher day of 58 kg.fisher/day. The CPUE in 2021–22 was the lowest since 2017–18 (51 kg.fisher/day) and was similar to the previous ten-year average (60 kg.fisher/hr). 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 biological stock is classified as a sustainablestock.

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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
Unspecified
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
Catch
South Australia
Commercial 57.99t
Indigenous Unknown
Recreational 251 t (2021–22)

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

Queensland – Commercial (Catch). Queensland commercial and charter data have been sourced from the commercial fisheries logbook program. Further information available through the Queensland Fisheries Summary Report https://www.daf.qld.gov.au/business-priorities/fisheries/monitoring-research/data/queensland-fisheries-summary-report

Queensland – Commercial (Management Methods). Harvest strategies available at: https://www.daf.qld.gov.au/business-priorities/fisheries/sustainable/harvest-strategy

Queensland – Recreational Fishing (Catch). Data are based at the whole of Queensland level and derived from statewide recreational fishing surveys. Where possible, estimates have been converted to weight (tonnes) using best known conversion multipliers. Conversion factors may display regional or temporal variability. In the absence of an adequate conversion factor, data presented as number of fish.

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

New South Wales – Recreational (Catch) . Recreational catch estimate of 20 t t is based on (i) an estimated recreational catch of 42,200 Blue Swimmer Crabs by NSW resident recreational anglers in 2019–20 [Murphy et al. 2021]; and (ii) an assumed mean weight of kept Blue Swimmer Crabs of 0.225 kg/crab.

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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 2023, Blue Crab (Portunus armatus) Fishery 2021/22. Fishery Assessment Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2007/000729-19. SARDI Research Report Series No. 1171. 51 pp.
  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. BMT 2018, Cockburn Sound-Drivers-Pressures-State-Impacts-Responses Assessment 2017 Final Report. Prepared for the Department of Water and Environmental Regulation, the Kwinana Industries Council, the City of Rockingham and the City of Kwinana on behalf of the Cockburn Sound Management Council by BMT Western Australia Pty Ltd. Report No. 1362_001/Rev1. Perth, Western Australia July 2018.
  4. 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.
  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. Chandrapavan, A, Caputi, N and 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).
  7. 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.
  8. 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.
  9. 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.
  10. 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.
  11. 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.
  12. Department of Primary Industries and Regional Development — DPIRD 2020b, Blue Swimmer Crab Resource of the South-West Western Australia Harvest Strategy 2020-2025 Version 1.0. Fisheries Management Paper No. 304. DPIRD, Western Australia.
  13. 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.
  14. 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.
  15. 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.
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  17. Hewitt, DE. Schilling, HT. Hanamseth, R. Everett, JD. Li, J. Roughan, M. Johnson, DD. Suthers, IM and Taylor, MD 2022 Mesoscale oceanographic features drive divergent patterns in connectivity for co-occurring estuarine portunid crabs. Fisheries Oceanography, 2022;31:587–600.
  18. Johnson, DD 2020, Status of Australian Fish Stocks 2020 – NSW Stock status summary – Blue Swimmer Crab (Portunus armatus).
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  22. Johnston, D, Harris, D, Yeoh, D and Blay, N 2021, West Coast Blue Swimmer Crab Resource Status Report 2021. In, Status Reports of the Fisheries and Aquatic Resources of Western Australia 2020/21.: The State the Fisheries. eds. Newman, S.J., Wise, B.S., Santoro, K.G. and Gaughan, D.J. Department of Primary Industries and Regional Development, Western Australia. pp 34-40.
  23. Johnston, D, Yeoh, D, Caputi, N and Harris, D (submitted), Stock recruitment-environment relationship of a portunid crab to assess stock decline: evidence of regime shift and implications for management.
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  25. 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.
  26. Johnston, DJ and Yeoh, DE 2021, Temperature drives spatial and temporal variation in the reproductive biology of the blue swimmer crab Portunus armatus A. Milne-Edwards, 1861 (Decapoda: Brachyura: Portunidae). Journal of Crustacean Biology. 41(3): 1-15
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  28. 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.
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  30. 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.
  31. 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.
  32. Marks, R, Hesp, A, Denham, A, Loneragan, N, Johnston, D and Hall, N 2021, Factors influencing the dynamics of a collapsed blue swimmer crab (Portunus armatus) population and its lack of recovery. Fish. Res., 242.
  33. Martell, S and Froese, R 2013, A simple method for estimating MSY from catch and resilience. Fish and Fisheries 14: 504-514.
  34. 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.
  35. Murphy, JJ, Ochwada-Doyle. FA, West. LD, Stark. KE, Hughes. JM and Taylor, MD 2022, Survey of recreational fishing in NSW, 2019/20 – Key Results. NSW DPI - Fisheries Final Report Series No. 161.
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  39. Queensland Department of Agriculture and Fisheries, Unpublished Data, Fishery Monitoring Database (QFSFRM). Viewed 13 July 2023. Brisbane, Queensland.
  40. Ryan, KL, Lai, EKM and Smallwood, CB 2022, Boat-based recreational fishing in Western Australia 2020/21. Fisheries Research Report No. 327 Department of Primary Industries and Regional Development, Western Australia. 221pp.
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  43. 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.
  44. 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.
  45. 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.
  46. Taylor, MD, Hewitt D, Hanemseth R, Schilling H, Nolan, S, Suthers, IM and Johnson, DD 2023, Informing adaptive management of portunid fisheries in NSW. Final Report to the Fisheries Resea,rch and Development Corporation on project 2017/006, NSW Department of Primary Industries, Port Stephens. CC BY 3.0
  47. Teixeira, D, Janes, R and Webley, J 2021, 2019–20 Statewide Recreational Fishing Survey Key Results. Project Report. State of Queensland, Brisbane.
  48. 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.

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