MUD CRABS (2020)

Scylla spp., Scylla serrata, Scylla olivacea

  • Thor Saunders (Department of Industry, Tourism and Trade, Northern Territory)
  • Daniel Johnson (Department of Primary Industries, New South Wales)
  • Danielle Johnston (Department of Primary Industries and Regional Development, Western Australia)
  • Lisa Walton (Department of Agriculture and Fisheries, Queensland)

Date Published: June 2021

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Two species of Mud Crabs are found in Australian waters: Giant Mud Crab and Orange Mud Crab. All six stocks are sustainable.

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Stock Status Overview

Stock status determination
Jurisdiction Stock Stock status Indicators
New South Wales Estuary General Fishery Sustainable

Catch, catch rate, biomass, fishing mortality

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Stock Structure

Two species of Mud Crabs are found in Australian waters: Giant Mud Crab (Scylla serrata) and Orange Mud Crab (S. olivacea). The former constitutes more than 99 per cent of the commercial catch of Mud Crabs in the Northern Territory and Queensland, and the entire commercial catch in New South Wales. The species composition in the Kimberley Developing Mud Crab Fishery (Western Australia) is uncertain but is known to vary considerably between locations.

The life history and biology of Giant Mud Crab in the Northern Territory and Queensland are well documented [Heasman 1980, Hill et al. 1984, Hill 1994, Knuckey 1999, Alberts-Hubatsch 2015] but, with some exceptions [Butcher et al. 2003, Butcher 2004, Alberts-Hubatsch et al. 2014], corresponding information from Western Australia and New South Wales is scarce. There are no published accounts on the biology of Orange Mud Crab in Australian waters. Hence, all catch, and biological information presented here refers to the Giant Mud Crab (S. serrata), unless otherwise stated.

Genetic evidence suggests that there are at least two biological stocks of Giant Mud Crab in Australian waters: one to the west and another to the south east of the Torres Strait [Gopurenko and Hughes 2002], referred to as the Northern Australian and East Coast biological stocks, respectively.

Female Giant Mud Crab in northern Australia migrate up to 95 km offshore to release their eggs [Hill 1994], which average around 4.5 million per individual [Mann et al. 1999]. Coupled with a planktonic larval stage that can last for several weeks [Nurdiani and Zeng 2007], this reproductive strategy may facilitate significant gene flow between areas (depending on local oceanography). However, there have been significant changes in the relative performance of some fisheries operating across these stocks since 2014, suggesting that, despite larval connectivity, there are different exploitation rates on components of the adult stock in different areas. These changes, combined with different management arrangements for each of the four jurisdictions that harvest Giant Mud Crab, and (in some cases) the need for more information on local population dynamics, and fine-scale stock structure, have resulted in this status report providing status determinations for Giant Mud Crab at the level of fishery management units: Kimberley Developing Mud Crab Fishery (Western Australia); Arnhem-West Mud Crab Fishery (Northern Territory), Western Gulf of Carpentaria (Northern Territory); Gulf of Carpentaria (Queensland), East Coast (Queensland); and the Estuary General Fishery (New South Wales).

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Stock Status

Estuary General Fishery

The Estuary General Fishery (New South Wales) (EGF) accounts for approximately 17 per cent of the commercial harvest from the East Coast Giant Mud Crab biological stock, with the annual catch composition by sex being very close to 1:1 (49 per cent female, 51 per cent male). A recent survey of recreational fishing in New South Wales (which may include some harvest by Indigenous fishers) indicated that the non-commercial take accounts for around 20 per cent of the overall Giant Mud Crab harvest in this state [Murphy et al. 2020] (using a regional weight multiplier estimated at 0.70 kg per crab).

Part of the Giant Mud Crab population in New South Wales is protected through a minimum size limit (85 mm CL) although the effectiveness of this measure is uncertain because the size at maturity of S. serrata in this jurisdiction is not known. Studies on the reproductive biology of S. serrata from different catchments in northern Australia have reported regional differences in size at sexual maturity [Knuckey 1999]. The life history of S. serrata in New South Wales may differ from populations elsewhere as this jurisdiction represents the southern limit of the species’ typical distribution on the eastern seaboard.

Several “no take” zones (applying to all marine organisms) along the New South Wales coast afford some protection to Giant Mud Crab and result in higher crab densities in the closed areas, size class distributions biased towards larger crabs, and spillover of crabs into adjacent fished areas [Butcher et al. 2003, Butcher et al. 2014]. However, these spatial closures are relatively small and fragmented, and their cumulative benefit on a fishery-wide scale has not been quantified.

Historically, the primary indicators for biomass and fishing mortality are commercial catch and standardised commercial catch rate (CPUE).  Standardised catch rates were predicted from generalised linear models (GLM). For recent data analysed as mean daily catch rates (available from 2009–10 to 2018–19), catch rates (zones combined) have remained stable and were above the 10-year average from 2013–14 to 2018–19 [Johnson 2020]. 

Catch-MSY model-assisted catch-only assessment [Martell and Froese 2013] was fitted to commercial catch from 1978–79 to 2018–19 using the 'simpleSA' package in R [Haddon et al. 2018]. Results of modified Catch-MSY modelling suggest that the current biomass of Giant Mud Crab in NSW waters is depleted to 53 per cent of the estimated maximum biomass with a 95 per cent confidence interval (CI) of 27–80 per cent [Johnson 2020]. Five-year stock projections at catch equal to the current total allowable commercial catch (~206 t) with recreational catches estimated at 20 per cent of total harvest, indicate that biomass is predicted to slowly decline [Johnson 2020].

In 2020, a Schaefer surplus production model (BSM) was fitted to commercial catch (1978–79 to 2018–19) and CPUE (1984–85 to 2018–19) using CMSY+ and BSM [Froese et al. 2019].  Based on BSM analysis, biomass in the last year (1 650 t, CI: 1 240–1 990 t) is estimated to be greater than Bmsy (1 390 t, CI: 910–2 130 t). Estimates of fishing mortality (F) and exploitation rate (F/Fmsy) in 2018–19 were 0.09 (CI: 0.07–0.12) and 0.95 (CI: 0.64–1.64), respectively [Johnson 2020]. All the above evidence indicates that the biomass of the management unit is unlikely to be depleted and that recruitment is unlikely to be impaired. The above evidence also 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 Estuary General Fishery (New South Wales) management unit is classified as a sustainable stock.

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Giant Mud Crab biology [Heasman 1980, Knuckey 1999, Butcher et al. 2003, Jebreen et al. 2008, Grubert and Lee 2013]

Species Longevity / Maximum Size Maturity (50 per cent)
MUD CRABS 3–4 years, 230 mm CW, but rarely exceeds 200 mm CW in most areas Varies by sex and location but generally 120–150 mm CW 
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Distribution of reported commercial catch of Mud Crabs
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Fishing methods
New South Wales
Mesh Net
Traps and Pots
Hand collection
Hook and Line
Dip Net
Traps and Pots
Hoop Net
Hand collection
Hook and Line
Dip Net
Traps and Pots
Hoop Net
Traps and Pots
Management methods
Method New South Wales
Gear restrictions
Possession limit
Size limits
Spatial closures
Catch limits
Effort limits
Gear restrictions
Limited entry
Protection of berried females
Size limit
Spatial closures
Spatial zoning
Customary fishing management arrangements
Gear restrictions
Possession limit
Protection of berried females
Size limit
Spatial closures
Spatial zoning
New South Wales
Commercial 119.38t
Indigenous Unknown
Recreational 37.9 t (2017–18)

Western Australia – Indigenous (catch) The estimate of the Indigenous harvest tonnage of Mud Crabs in Western Australia has been revised down as the weight multiplier previously used to calculate this value (1.34 kg per crab) is now considered unrealistically high given that the average weight of harvested Mud Crabs in Western Australia was recently estimated at 0.65 kg.

Northern Territory — Charter (management methods) In the Northern Territory, charter operators are regulated through the same management methods as the recreational sector but are subject to additional limits on license and passenger numbers.

Northern Territory – Indigenous (management methods) The Fisheries Act 1988 (NT), specifies that “…without derogating from any other law in force in the Territory, nothing in a provision of this Act or an instrument of a judicial or administrative character made under it limits the right of Aboriginals who have traditionally used the resources of an area of land or water in a traditional manner from continuing to use those resources in that area in that manner”.

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) Murphy et al. [2020].

Active Vessels The number of active exemption holders (for Western Australia), licences (for the Northern Territory and Queensland) or businesses (for New South Wales) are shown here because the number of active vessels is not an appropriate measure of effort in Australian Mud Crab fisheries. Licensing arrangements also vary significantly between jurisdictions.

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Catch Chart

Commercial catch of Mud Crabs - note confidential catch not shown
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  1. Alberts-Hubatsch, H 2015, Movement patterns and habitat use of the exploited swimming crab Scylla serrata (Forskål, 1775), PhD thesis, University Bremen, Germany.
  2. Alberts-Hubatsch, H, Lee SY, Diele, K, Wolff, M and Nordhaus, I 2014, Microhabitat use of early benthic stage mud crabs, Scylla serrata (Forskål, 1775), in eastern Australia. Journal of Crustacean Research, 34: 604–610.
  3. Atlas of Living Australia website. Species page: https://bie.ala.org.au/species/urn:lsid:biodiversity.org.au:afd.taxon:628cd52f-10b6-4f23-8a76-9caff511b775#tab_recordsView. Accessed 20 January 2021
  4. Benthuysen, JA, Oliver, ECJ, Feng, M and Marshall, AG 2018, Extreme marine warming across tropical Australia during austral summer 2015–2016. Journal of Geophysical Research: Oceans, 123: 1301–1326.
  5. Brown, IW 2010, Taking female Mud Crabs (Scylla serrata): assessment of risks and benefits, FRDC final report 2009/031, Queensland Government Department of Employment, Economic Development and Innovation, Deception Bay.
  6. Butcher PA, Boulton AJ, Macbeth WG and Malcolm HA (2014) Long-term effects of marine park zoning on giant mud crab Scylla serrata populations in three Australian estuaries, Marine Ecology Progress Series 508: 163–176.
  7. Butcher, PA 2004, Mud Crab (Scylla serrata) and marine park management in estuaries of the Solitary Islands Marine Park, New South Wales, PhD thesis, University of New England, Armidale.
  8. Butcher, PA, Boulton, AJ and Smith, SDA 2003, Mud Crab (Scylla serrata: Portunidae) populations as indicators of the effectiveness of estuarine marine protected areas, In JP Beumer, A Grant and DC Smith (eds.), Aquatic protected areas: what works best and how do we know? Proceedings of the world congress on aquatic protected areas, Australian Society for Fish Biology, Cairns, Queensland, 421–427.
  9. COA BOM (Commonwealth of Australia, Bureau of Meteorology) 2017, Northern Territory wet season October to April 2016–17: wetter than average.
  10. COA BOM (Commonwealth of Australia, Bureau of Meteorology) 2018, Regional Water Information.
  11. Coleman, APM 2004, The national recreational fishing survey: the Northern Territory, Fishery report 72, Northern Territory Department of Business, Industry and Resource Development, Darwin.
  12. Duke, NC, Kovacs, JM, Griffiths, AD, Preece, L, Hill, DJE, van Oosterzee, P, Mackenzie, J, Morning, HS and Burrows, D 2017, Large-scale dieback of mangroves in Australia. Marine and Freshwater Research 68:1816–1829.
  13. Froese, R. Demirel, N and Winker, H 2019, Simple User Guide for CMSY+ and BSM (CMSY_2019_9f.R) published online at http://oceanrep.geomar.de/33076/
  14. Froese, R. Demirel, N. Gianpaolo, C. Kleisner, KM and Winker, H 2017, Estimating Fisheries Reference Points from Catch and Resilience. Fish and Fisheries 18: 506-526.
  15. Gopurenko, D and Hughes JM 2002, Regional patterns of genetic structure among Australian populations of the mud crab Scylla serrata (Crustacea: Decapoda): evidence from mitochondrial DNA, Marine and Freshwater Research, 53: 849–857.
  16. Grubert MA, Walters CJ, Buckworth, RC and SS Penny. In press, Simple modelling to inform harvest strategy policy for a data moderate crab fishery. Marine and Coastal Fisheries.
  17. Grubert, M, D Johnson, D Johnston, and M Leslie 2016, Mud Crabs. in Status of Australian Fish Stocks Reports 2016.
  18. Grubert, M. A., Walters, C. J., Buckworth, R. C., & Penny, S. S. (2019). Simple Modeling to Inform Harvest Grubert, M. A., Walters, C. J., Buckworth, R. C., & Penny, S. S. (2019). Simple Modelling to Inform Harvest Strategy Policy for a Data-Moderate Crab Fishery. Marine and Coastal Fisheries, 11(2), 125-138.
  19. Grubert, MA and Lee, HS 2013, Improving gear selectivity in Australian Mud Crab fisheries, Fishery report 112, Northern Territory Government Department of Primary Industry and Fisheries, Darwin.
  20. 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.
  21. Heasman, MP 1980, Aspects of the general biology and fishery of the Mud Crab Scylla serrata (Forskål), in Moreton Bay, Queensland, PhD thesis, University of Queensland, Brisbane.
  22. Henry, GW and Lyle, JM (eds.) 2003, The national recreational and Indigenous fishing survey, Fisheries Research Development Corporation project 99/158, Australian Government Department of Agriculture, Fisheries and Forestry, Canberra.
  23. Hill, BJ 1994, Offshore spawning by the portunid crab Scylla serrata (Crustacea Decapoda), Marine Biology, 120: 379–384.
  24. Hill, BJ, Williams, MJ and Dutton, P 1982, Distribution of juvenile, subadult and adult Scylla serrata on tidal flats in Australia, Marine Biology, 69: 117–120.
  25. Hyland, SJ, Hill, BJ and Lee, CP 1984, Movement within and between different habitats by the portunid crab Scylla serrata. Marine Biology, 80: 57–61.
  26. Ikhwanuddin, M, Azmiea, G, Juariah, HM, Zakaria, MZ and Ambak, MA 2011, Biological information and population features of mud crab, genus Scylla from mangrove areas of Sarawak, Malaysia. Fisheries Research 108: 299–306.
  27. Integrated Marine Observing System 2018, IMOS OceanCurrent: Surface Currents and Temperature. Up to date ocean information around Australia.
  28. Jebreen, E, Helmke, S, Lunow, C, Bullock, C, Gribble, N, Whybird, O and Coles, R 2008, Fisheries long term monitoring program—Mud Crab (Scylla serrata) report: 2000–2002, PR08-3498, Queensland Government Department of Primary Industries and Fisheries, Brisbane.
  29. 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.
  30. Keenan CP, Davies PJF and Mann DL 1998, A revision of the genus Scylla de Haan, 1833 (Crustacea: Decapoda: Brachyura: Portunidae). The Raffles Bulletin of Zoology ,46: 217–245.
  31. Knuckey, IA 1999, Mud Crab (Scylla serrata) population dynamics in the Northern Territory, Australia and their relationship to the commercial fishery, PhD thesis, Northern Territory University, Darwin.
  32. Mann, D, Asakawa, T and Blackshaw, A 1999, Performance of mud crab Scylla serrata broodstock held at Bribie Island Aquaculture Research Centre, In CP Keenan and A Blackshaw (eds), Mud Crab aquaculture and biology, Proceedings of an international scientific forum held in Darwin, Australia, 101–105, ACIAR Proceedings No. 78.
  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, J.J., Ochwada-Doyle, F.A., West, L.D., Stark, K.E. and Hughes, J.M., 2020. The NSW Recreational Fisheries Monitoring Program - survey of recreational fishing, 2017/18. NSW DPI - Fisheries Final Report Series No. 158.
  35. Northrop, A, O'Neill, M, F and Robins, J 2019 Towards an initial quota for the Queensland mud crab fishery. Department of Agriculture and Fisheries. Brisbane, Queensland.
  36. NTG (Northern Territory Government) 2017, Management Framework for the Northern Territory Mud Crab Fishery 2017. Northern Territory Department of Primary Industry and Resources, Darwin.
  37. NTG (Northern Territory Government) 2018, Status of Key Northern Territory Fish Stocks Report 2016. Northern Territory Department of Primary Industry and Resources, Fishery Report 119, Darwin.
  38. Nurdiani, R and Zeng, CS 2007, Effects of temperature and salinity on the survival and development of Mud Crab, Scylla serrata (Forskål), larvae. Aquaculture Research, 38: 1529–1538.
  39. Pillans, S, Pillans, RD, Johnstone, RW, Kraft, PG, Haywood, MDE and Possingham, HP 2005, Effects of marine reserve protection on the Mud Crab Scylla serrata in a sex-based fishery in subtropical Australia. Marine Ecology Progress Series, 295: 201–213.
  40. QFish, Department of Agriculture and Fisheries, www.qfish.gov.au
  41. 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.
  42. Schiller, A 2011, Ocean circulation on the North Australian Shelf, Continental Shelf Research, 31: 1087–1095.
  43. Status of Australian Fish Stocks 2020 – NSW Stock status summary – Giant Mud Crab (Scylla serrata).
  44. 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.
  45. Taylor, S, Webley, J and McInnes, K 2012, 2010 statewide recreational fishing survey, Queensland Department of Agriculture, Fisheries and Forestry, Brisbane.
  46. The Atlas of Living Australia 2018, Spatial Data Portal.
  47. Walters, CJ 2007, User guide for stock assessment using GTGmodel. Fisheries Centre, University of British Columbia publication, 10 p.
  48. Webley, J, McInnes, K, Teixeira, D, Lawson, A and Quinn, R 2015, Statewide Recreational Fishing Survey 2013–14, State of Queensland, Department of Agriculture and Fisheries.
  49. West, LD, Lyle, JM, Matthews, SR and Stark, KE 2012, A survey of recreational fishing in the Northern Territory, 2009–10, Fishery report 109, Northern Territory Government Department of Resources, Darwin.
  50. 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, Fisheries final report series 149, New South Wales Government Department of Primary Industries, Sydney.
  51. Wolanski, E 1993, Water circulation in the Gulf of Carpentaria. Journal of Marine Systems 4: 401–420.

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