*

Giant Crab occurs from WA to TAS with weakly connected stocks throughout this range. The stock associated with each cluster of fishing is assessed here. The Western Australian and South Australian stocks are sustainble. The stock West of Bass Strait is recovering. The stock East of Tasmania is undefined due to limited fishing and data.

Giant Crab is continuously distributed across its range from Western Australia to East of Tasmania. Movement of giant crab post-settlement is limited. Planktonic larval duration is around 50 days, with larval release occurring along the edge of the continental shelf. The shelf is a high current area, facilitating dispersal, and oceanographic modelling has indicated that Giant Crab dispersal occurs over reasonably large spatial scales [Gardner 1998; Gardner and Quintana 1998; Williams et. al. 2009]. However, given the large spatial scale of the distribution and features that disrupt dispersal (such as the Bass Strait) the species is likely to consist of a series of local populations with moderate connectivity within the meta population. An FRDC project is currently underway which will provide further clarification on stock structure for future assessments (FRDC Project 2021-025 Resolving the biological stock structure of Southern Ocean crab fisheries).

Fishing occurs in four spatial clusters which are sufficiently separated that each cluster is likely to be fishing a local stock that has a low level of connectivity with the other stocks. The stock "West of Bass Strait" is fished by both Victoria and Tasmania. This stock previously had differing assessments for the two jurisdictions which resulted in an assessment on a jurisdictional basis. However, these differences have now been resolved. Consequently, assessment of stock status is presented here at the biological-stock level—Eastern Tasmania, South Australia, West of Bass Strait, and Western Australia.

West of Bass Strait

The stock West of Bass Strait is fished by both the Victorian and Tasmanian fisheries. Both fisheries are regulated through a TACC and minimum legal lengths of 140 mm for males and 150 mm for females. The size limit was supported by a length-based model which was developed for the Tasmanian fishery with size limits affording protection to mature female crabs, which are also protected whilst berried and through female spawning closures [Gardner et. al. 2007]. In Victoria the size limit aims to ensure that egg production remains at no less than 40% of unfished levels [McGarvey et al. 1999]. However, there is considerable uncertainty around the growth rates and sizes at maturity of larger females and hence in the degree of protection provided by these limits.

The standardised CPUE in the Tasmanian fishery on this stock declined by approximately 75% from the fishery's inception in 2000-01 to the most recent assessment in 2021–22, despite significant reductions in the statewide TACC from 103.5 t to 20.7 t. This equated to a reduction in catch for the West of Bass Strait stock from a peak of 68 t to 17 t. The stock assessment model has not been used since 2013–14 due to a lack of length-frequency data, however in that year egg production had decreased to an estimated 14% of unfished levels in 2013–14 [Emery et. al. 2015]. This level of egg production is considered inadequate relative to benchmarks in most crustacean fisheries [Fogarty and Gendron 2004]. Due to its slow growth and longevity, Giant Crab is particularly susceptible to becoming recruitment overfished.

The Victorian fishery is smaller and despite an initial peak of over 200 t in 1992–93 [Fisheries Victoria 2010] has been at or below 10 t for the last ten years. Standardised CPUE for this fishery is a less reliable indicator of abundance due to the small size of the fishery and changing operator characteristics over time – notably a shift from rock lobster vessels taking some Giant Crab to a single dedicated Giant Crab operator in recent years. A re-evaluation of CPUE has indicated that CPUE in the last eight years was lower than previously thought and may have been at the limit reference point during this period [VFA 2020]. Previous evidence indicates that the biomass of this stock is likely to be depleted and that recruitment is likely to be impaired. 

Significant ongoing catch reductions have taken place in both jurisdictions, resulting in a decrease from 82 t in 2000–01 to 22 t in 2020–21. Despite these reductions the standardised CPUE continued to fall in Tasmania and in Victoria after a period of higher levels in the 2000s returned to record low levels. This ongoing lack of response in CPUE to significant catch reductions over the last decade led to a high level of concern, particularly in Tasmania where this reduction was more pronounced. In both the Tasmanian and Victorian fisheries there has been an increase in CPUE in the most recent year (2021–22). However, in both assessments there is concern about the reliability of standardised CPUE due to the small number of operators. Consequently, there is not yet definitive evidence to indicate recovery is taking place. The above evidence indicates that current fishing mortality is constrained by management to a level that should allow the stock to recover from its recruitment impaired state; however measurable improvements are yet to be detected. 

On the basis of the evidence presented above, the Giant Crab Fishery (Victoria/Tasmania) management unit is classified as a depleted stock.

Giant Crab biology [Gardner 1998; McGarvey et. al. 1999; Williams et. al. 2009,]

Distribution of reported commercial catch of Giant Crab

South Australian data are from quota holders in the 2016–17 fishing season (October 2016–May 2017), Victorian data are for the 2021–22 fishing season (November 2021–September 2022), Tasmanian data are for the 2022-23 fishing season (March 2022 – February 2023) and South Coast Crustacean Managed Fishery (Western Australia) data are for the 2019–20 financial year. 

Victoria – Indigenous (Management Methods). A person who identifies as Aboriginal or Torres Strait Islander is exempt from the need to obtain a Victorian recreational fishing licence, provided they comply with all other rules that apply to recreational fishers, including rules on equipment, catch limits, size limits and restricted areas. Traditional (non-commercial) fishing activities that are carried out by members of a traditional owner group entity under an agreement pursuant to Victoria’s Traditional Owner Settlement Act 2010 are also exempt from the need to hold a recreational fishing licence, subject to any conditions outlined in the agreement. Native title holders are also exempt from the need to obtain a recreational fishinglicence under the provisions of the Commonwealth’s Native Title Act 1993.

Commercial catch of Giant Crab - note confidential catch not shown

1. Emery, T, Hartmann, K and Gardner, C 2015, Giant Crab stock assessment report 2013/14, IMAS, Hobart.
2. Fisheries Victoria 2010, Giant Crab Management Plan, Second Edition, ISBN 978-1-74264-478-3.
3. Fogarty, MJ and Gendron, L 2004, Biological reference points for American lobster (Homarus americanus) populations: limits to exploitation and the precautionary approach, Canadian Journal of Fisheries and Aquatic Sciences, 61(8): 1392–1403.
4. Gardner, C 1998, First record of larvae of the Giant Crab Pseudocarcinus gigas in the plankton, Papers and Proceedings of the Royal Society of Tasmania, 132: 47–48.
5. Gardner, C and Quintana, R 1998, Larval development of the Australian Giant Crab Pseudocarcinus gigas (Lamarck, 1818) (Decapoda: Oziidae) reared in the laboratory, Journal of Plankton Research, 20(6): 1169–1188.
6. Gardner, C, Haddon, M, Hobday,D and McGarvey, R 2007, Development of the tools for long term management of the Giant Crab resource: data collection methodology, stock assessment and harvest strategy evaluation, final report to the Fisheries Research and Development Corporation, Canberra.
7. McGarvey, R, Matthews, JM and Levings, AH 1999, Yield-, value-, and egg-per-recruit of Giant Crab, Pseudocarcinus gigas, South Australian Research and Development Institute, Adelaide.
8. McLeay, L 2023, Stock status report for the South Australian South Australian Giant Crab (Pseudocarcinus gigas) Fishery in 2021/22. Fishery Status Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2011/000332-12. SARDI Research Report Series No. 1173.
9. PIRSA 2018, Management Policy for Commercial Fishing of Giant Crabs in South Australia. Primary Industries and Regions South Australia. Adelaide, Australia.
10. VFA 2020, 2018/19 Victorian Giant Crab Stock Assessment. Victorian Fisheries Authority Report Series No.11
11. Williams, A, Gardner, C, Althaus, F, Barker, B and Mills, D 2009, Understanding shelf-break habitat for sustainable management of fisheries with spatial overlap, final report to the Fisheries Research and Development Corporation, project 2004/066, CSIRO Marine and Atmospheric Research, Hobart.