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Stock Status Overview
|South Australia||Southern Australia||LCF, MSF||Sustainable||Biomass (pup production), catch|
- Lakes and Coorong Fishey (SA)
- Marine Scalefish Fishery (SA)
Gummy Shark (Mustelus antarcticus) is distributed throughout the temperate waters of Australia, from at least Port Stephens in New South Wales, to Geraldton in Western Australia (including Tasmania)1,2. The most recent research on biological stock structure for Gummy Shark3 suggests there is most likely one biological stock in southern Australia (extending from the lower west coast of Western Australia to Jervis Bay in New South Wales) and a second biological stock in eastern Australia (extending from Newcastle to the Clarence River in New South Wales). The Southern Australian biological stock is considered to comprise four separate subpopulations for formal stock assessment purposes: the continental shelf of Bass Strait, Tasmania, South Australia and Western Australia. The first three are assessed by the Commonwealth, within an integrated assessment by the Shark Resource Assessment Group4,5. Due to management differences and the way the stock is modelled, the fourth is assessed separately by Western Australia6.
Here, assessment of stock status is presented at the biological stock level—Southern Australian and Eastern Australian.
The Bass Strait, Tasmania and South Australia components of the stock were assessed using a sex and age structured model5. The most recent assessment5 treats Bass Strait, South Australia and Tasmania as separate subpopulations, with no movement of animals between these regions and no density-dependent effects of one population on another. Gillnet closures off South Australia have been implemented to reduce interactions with marine mammals (particularly Australian Sea Lions and dolphins), including buffers around breeding colonies and trigger limits, with observed levels of bycatch above the trigger limits resulting in an 18 month closure of larger areas7. These closures have reduced catch and catch per unit effort (CPUE) off South Australia. As a result of the large changes in operating conditions, the South Australian CPUE data after 2010 was considered to be a poor indicator and was not included in the assessment. The South Australian closures may have also reduced the CPUE off Victoria, as operators moved from South Australia to Victoria5. However, as these impacts were considered minor, catch and CPUE data up to 2012 from Victoria (and Tasmania) were retained in the model.
There is a close relationship between the number of pups and both the number, and length, of females4 and so the Commonwealth assessment uses pup production as an indicator of biomass. The assessment estimated pup production to be more than 48 per cent of the unfished level of pup production (1927) for all three Gummy Shark populations5. Some model sensitivities that explored density dependence estimated pup production to be as low as 31 per cent (for the Bass Strait population)5, which is below the target reference point for the Commonwealth Harvest Strategy Policy, but above the limit reference point. These results indicate that the three populations examined (Bass Strait, South Australia and Tasmania) are unlikely to be recruitment overfished8.
The stock assessment gave a recommended biological catch of 2010 tonnes (t) however; this was above the historical average catch for the fishery. As a result, the Commonwealth Shark Resource Assessment Group recommended retaining the (lower) 2013–14 total allowable catch (TAC) of 1836 t for the 2014–15 to 2016–17 seasons, as a 3-year (multi-year) TAC9. Total combined commercial catch (state and Commonwealth) for the three subpopulations in 2015 was 1780 t. This level of fishing pressure is unlikely to cause this part of the biological stock to become recruitment overfished8.
The Western Australian component of the stock was assessed using an age structured model developed in the mid-1990s to estimate total and breeding stock biomass10. Since then, catches and CPUE have been monitored in reference to those biomass estimates. A new assessment model incorporating movement rates within Western Australian waters is due to be completed by 2016.
The most recent assessment6 concluded that reductions in demersal gillnet fishing effort since biomass was estimated to be 42.7 per cent of the unfished (1975) level, in 1997–98, should have ensured that biomass has remained above this level. Therefore, this part of the biological stock is not considered to be recruitment overfished.
These conclusions are supported by an increasing trend in standardised CPUE between the mid-1990s and 2005–06. This is thought to be the result of reductions in demersal gillnet fishing effort in Western Australia from 1992 onwards, leading to increases in breeding stock biomass. A subsequent increase in CPUE to unprecedented levels, peaking in 2007–08, was followed by a rapid decline to 2011–12 and an increase between 2012–13 and 2013–14. The CPUE in 2011–12 was still at historically high levels. Despite the recent unusual spike and subsequent decline in CPUE, current levels of fishing pressure are unlikely to cause this part of the biological stock to become recruitment overfished6.
On the basis of the evidence provided above, the Southern Australian biological stock is classified as a sustainable stock.
Gummy Shark biology4,12–14
|Species||Longevity / Maximum Size||Maturity (50 per cent)|
|Gummy Shark||16 years; 1 850 mm TL (25 kg total body mass)||Females: 1 105–1 253 mm TL Males: 950–1 133 mm TL|
Distribution of reported commercial catch of Gummy Shark
|Hand Line, Hand Reel or Powered Reels|
|Coastal, Estuary and River Set Nets|
|Hand Line, Hand Reel or Powered Reels|
|143 in MSF|
- Marine Scalefish Fishery (SA)
|Commercial||85.55t in MSF|
|Recreational||11 597 individuals caught in 2013–14 (of which, 8822 were kept)|
- Marine Scalefish Fishery (SA)
a New South Wales Data provided for New South Wales align with the 2015 calendar year with all vessels active in the fishery included (irrespective of whether they reported landing this species). The New South Wales EGF, OTF and OTLF fish both the Southern Australian and Eastern Australian stocks
b Commonwealth – Recreational The Australian Government does not manage recreational fishing in Commonwealth waters. Recreational fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters, under its management regulations.
c Commonwealth – Indigenous The Australian Government does not manage non-commercial Indigenous fishing in Commonwealth waters, with the exception of the Torres Strait. In general, non-commercial Indigenous fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters.
d Victoria – Indigenous In Victoria, regulations for managing recreational fishing are also applied to fishing activities by Indigenous people. Recognised Traditional Owners (groups that hold native title or have agreements under the Traditional Owner Settlement Act 2010 [Vic]) are exempt (subject to conditions) from the requirement to hold a recreational fishing licence, and can apply for permits under the Fisheries Act 1995 (Vic) that authorise customary fishing (for example, different catch and size limits or equipment). The Indigenous category in Table 3 refers to customary fishing undertaken by recognised Traditional Owners. In 2015, there were no applications for customary fishing permits to access Gummy Shark.
e New South Wales – Indigenous Aboriginal Cultural Fishing Interim Access Arrangement - allows an Aboriginal 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 themselves.
f New South Wales – Indigenous 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 37 (1)(c1), Aboriginal cultural fishing authority.
h Tasmania – Recreational (management methods) In Tasmania, a recreational licence is required for fishers using dropline or longline gear, along with nets, such as gillnet or beach seine.
i Tasmania – Indigenous In Tasmania, Indigenous people engaged in aboriginal fishing activities in marine waters are exempt from holding recreational fishing licences, but must comply with all other fisheries rules as if they were licensed. Additionally, recreational bag and possession limits also apply. If using pots, rings, set lines or gillnets, Aborigines must obtain a unique identifying code (UIC). The policy document Recognition of Aboriginal Fishing Activities for issuing a Unique Identifying Code (UIC) to a person for Aboriginal Fishing activity explains the steps to take in making an application for a UIC.
j Victoria – Indigenous Subject to the defence that applies under Section 211 of the Native Title Act 1993 (Cth), and the exemption from a requirement to hold a Victorian recreational fishing licence, the non-commercial take by indigenous fishers is covered by the same arrangements as that for recreational fishing.
Commercial catch of Gummy Shark - note confidential catch not shown
Effects of fishing on the marine environment
- Interactions with marine mammals (Australian Sea Lions, Australian Fur Seals, Long-nosed Fur Seals and dolphins) in some gillnet fisheries continue to be an issue. Mitigation actions that have been implemented include spatial and temporal closures, increased monitoring17 and implementation of the Australian Sea Lion Management Strategy7and Dolphin Strategy18. The Australian Fisheries Management Authority has closed areas where most interactions occur and increased observer coverage to 100 per cent in adjacent areas. These management measures were revised through the Dolphin Strategy for the 2014–15 fishing season18.
- Offal management strategies, introduced in April 2011, include requirements for gillnet operators to remove any biological materials from nets before they are set. This has been effective in reducing seabird interactions in other fisheries17.
- The use of auto-longlines in the Southern and Eastern Scalefish and Shark Fishery (Gillnet Hook and Trap Sector) has raised concerns about the potential for interactions with seabirds, including albatrosses and shearwaters19. New measures have been implemented to assist industry to meet the Seabird Threat Abatement Plan20 and Performance Criteria21.
- Demersal gillnets are known to interact with a number of threatened and protected species, including marine mammals and seabirds, in areas of Western Australia where they are used to catch Gummy Shark. However, such interactions occur at a very low frequency and have been assessed as posing low–negligible risks to these populations6.
- Recent analysis of potential changes in ecosystem structure of finfish in the South and West Coast Bioregions of Western Australia22 found no evidence of any systematic change in species diversity or richness, or trophic index, indicating that the Western Australian fisheries are not having a measurable impact on the food chain or trophic structure in these regions.
Environmental effects on Gummy Shark
- Sea level rise and changes in sea temperature associated with climate change may negatively affect Gummy Shark stocks because the habitats that Gummy Shark use as nursery and feeding grounds are potentially sensitive to such effects23. Habitat modification, for example through installation of pipelines and outfalls, construction of piers, sewerage and industrial outlets, and land run-off may also affect nursery/pupping grounds23.
- 1 Gardner, MG and Ward, RD 2002, Taxonomic affinities within Australian and New Zealand Mustelus sharks inferred from allozymes, mitochondrial DNA and precaudal vertebrae counts, Copeia, 2002(2): 356–363.
- 2 Last, PR and Stevens, JD 2009, Sharks and rays of Australia, CSIRO Publishing, Collingwood.
- 3 White, WT and Last, PR 2008, Description of two new species of gummy sharks, genus Mustelus (Carcharhiniformes: Triakidae), from Australian waters, in PR Last, WT White and JJ Pogonoski (eds), Descriptions of new Australian chondrichthyans, CSIRO Marine and Atmospheric Research paper 22, CSIRO Marine and Atmospheric Research, Canberra, 189–202.
- 4 Shark Resource Assessment Group 2012, 2011 stock assessment report for Gummy Shark (Mustelus antarcticus), prepared by the Shark Resource Assessment Group (SharkRAG), Australian Fisheries Management Authority, Canberra.
- 5 Thomson, R and Sporcic, M 2013, Gummy Shark assessment update for 2013, using data to the end of 2012 (DRAFT): December 2013, CSIRO, Hobart.
- 6 McAuley, R, Braccini, M, Newman, SJ and O’Malley, JO 2015, Temperate Demersal Gillnet and Longline Fisheries status report, in WJ Fletcher and K Santoro (eds), Status reports of the fisheries and aquatic resources of Western Australia 2014/15, Western Australian Department of Fisheries, Perth, 261–272.
- 7 Australian Fisheries Management Authority 2010, Australian Sea Lion Management Strategy: Southern and Eastern Scalefish and Shark Fishery (SESSF), AFMA, Canberra.
- 8 Marton, N and Savage, J 2015, Shark Gillnet and Shark Hook sectors, in H Patterson, L Georgeson, I Stobutzki and R Curtotti (eds), Fishery status reports 2015, Australian Bureau of Agricultural and Resource Economics and Sciences, Canberra, 244–267.
- 9 Australian Fisheries Management Authority 2013, Species summaries for the Southern and Eastern Scalefish and Shark Fishery: for stock assessments completed in 2013 in preparation for the 2014–15 fishing season, AFMA, Canberra.
- 10 Simpfendorfer, C, Lenanton, R and Unsworth, P 1996, Stock assessment of large coastal demersal sharks, final report to the Fisheries Research and Development Corporation, FRDC project 93/067, FRDC, Canberra.
- 11 Rowling, K, Hegarty, A and Ives, M 2010, Gummy Shark (Mustelus antarcticus), in K Rowling, A Hegarty and M Ives (eds), Status of fisheries resources in NSW 2008/09, Industry and Investment New South Wales, Cronulla, 392.
- 12 Moulton, PM, Walker, TI and Saddlier, SR 1992, Age and growth studies of Gummy Shark, Mustelus antarcticus (Günther), and school shark, Galeorhinus galeus (Linnaeus), from southern-Australian waters, Australian Journal of Marine and Freshwater Research, 43: 1241–1267.
- 13 Walker, TI 2007, Spatial and temporal variation in the reproductive biology of Gummy Shark Mustelus antarcticus (Chondrichthyes: Triakidae) harvested off southern Australia, Marine and Freshwater Research, 58: 67–97.
- 14 Walker, TI 2010, Population biology and dynamics of the Gummy Shark (Mustelus antarcticus) harvested off southern Australia, PhD thesis, University of Melbourne.
- 15 Ryan, KL, Wise, BS, Hall, NG, Pollock, KH, Sulin, EH and Gaughan, DJ 2013, An integrated system to survey boat-based recreational fishing in Western Australia 2011/12, Fisheries research report 249, Western Australian Department of Fisheries, Perth.
- 16 Jones, GK 2009, South Australian Recreational Fishing Survey, South Australian fisheries management series 54, Primary Industries and Resources South Australia, Adelaide.
- 17 Australian Fisheries Management Authority 2011, Fisheries Management (Southern and Eastern Scalefish and Shark Fishery management plan 2003) Temporary Order 2011, AFMA, Canberra.
- 18 Australian Fisheries Management Authority 2014, Dolphin strategy: minimising dolphin bycatch, AFMA, Canberra.
- 19 Knuckey, I, Ciconte, A, Koopman, M, Hudson, R and Rogers, P 2014, Trials of longlines to target Gummy Shark in SESSF Waters off South Australia, Fisheries Research and Development Corporation, project 2011/068, produced by Fishwell Consulting, Queenscliff.
- 20 Commonwealth of Australia 2014, Threat Abatement Plan 2014 for the incidental catch (or bycatch) of seabirds during oceanic longline fishing operations, Department of the Environment, Canberra
- 21 Australian Fisheries Management Authority 2014, New measures to protect seabirds in SESSF auto-longline fisheries, AFMA, Canberra.
- 22 Hall, NG and Wise, BS 2011, Development of an ecosystem approach to the monitoring and management of Western Australian fisheries, report to the Fisheries Research and Development Corporation, project 2005/063, Fisheries research report 215, Western Australian Department of Fisheries, Perth.
- 23 Hobday, AJ, Poloczanska, ES and Matear, RJ 2007, Climate impacts on Australian fisheries and aquaculture: implications for the effects of climate change, report to the Department of Climate Change, Canberra.