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Stock Status Overview
|Northern Territory||Western Australia||ONLF||Transitional-recovering||Catch, CPUE , fishing mortality|
- Offshore Net and Line Fishery (NT)
Sandbar Shark (Carcharhinus plumbeus) occurs primarily off both the east and west coasts of Australia, from approximately latitude 17–32°S off the east coast, and latitude 13–36°S off the west coast1,2. The species is also encountered off the northern Australian coast, although in much lower numbers. In addition to genetic analysis that suggests limited gene flow between eastern and western Sandbar Shark stocks3, there are limited recorded catches in the Gulf of Carpentaria and southern Australia. Thus, the species is considered to be represented by separate Eastern and Western biological stocks in Australian waters.
Here, assessment of stock status is presented at the biological stock level—Western Australian and Eastern Australian.
In Western Australia, Sandbar Shark is targeted by the West Coast Demersal Gillnet and Demersal Longline Fishery, and taken in lesser quantities by the Joint Authority Southern Demersal Gillnet and Demersal Longline Managed Fishery4. It was also previously targeted by the Western Australian North Coast Shark Fishery5. The Western Australian stock assessment uses current and historical data from all of these fisheries. Minor catches historically reported from the Offshore Net and Line Fishery (Northern Territory) are assumed to be from the Western Australian biological stock, as is an unquantified catch from the Memorandum of Understanding Box Shark Fishery6. These are not explicitly included in assessments of this stock.
Given the longevity of Sandbar Shark (30–40 years) and the age-specific nature of targeted fishing mortality (mostly between 2 and 10 years of age), a sufficiently long time-series of catch per unit effort data is not yet available for dynamic stock assessment modelling. Assessment of this stock has therefore been undertaken using empirically derived estimates of fishing mortality between 2001 and 2004, and demographic modelling techniques7,8. Demographic modelling indicated that combined levels of fishing mortality in Western Australian targeted shark fisheries, non-target commercial fisheries and the recreational fishing sector became increasingly unsustainable between 2001 and 2004 (when catches peaked at 918 tonnes [t]) and had probably exceeded sustainable levels since 1997–98. These conclusions are supported by fishery-independent survey data that indicated declining breeding stock abundance between 2002 and 20055,7.
Since 2010, Sandbar Shark catches have remained well below the levels that will allow a gradual recovery of the breeding stock4. The expected reductions in recruitment from previously excessive exploitation of the breeding stock are likely to be ameliorated by significant reduction in targeted fishing effort. Therefore, although the breeding stock is considered to be close to the minimum acceptable limit (40 per cent of unfished biomass), current levels of fishing are considered suitably precautionary to ensure the recovery of this biological stock4.
The above evidence indicates that this stock was subjected to overfishing. However, since 2010 these indicators suggest a recovering stock. In addition, the above evidence indicates that the current level of fishing pressure should allow the stock to recover4.
On the basis of the evidence provided above, the Western Australian biological stock is classified as a transitional–recovering stock.
|Species||Longevity / Maximum Size||Maturity (50 per cent)|
|Sandbar Shark||30–40 years; 1 660 mm FL; 2 150 mm TL||Females: 16.2 years; 1 360 mm FL Males: 13.8 years; 1 270 mm FL|
Sandbar Shark biology2,11,12
Distribution of reported commercial catch of Sandbar Shark
|Hand Line, Hand Reel or Powered Reels|
|0 in ONLF|
- Offshore Net and Line Fishery (NT)
|Indigenous||Unknown but likely to be negligible|
|Recreational||Unknown but likely to be negligible|
Indigenousa‒d Recreational/Indigenous (catch)e
a Under the Fisheries Act 1994 (Qld), Indigenous fishers in Queensland are able 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.
b The Aboriginal 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 themselves.
c 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.
d 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 recreational fishing licence, the non-commercial take by indigenous fishers is covered by the same arrangements as that for recreational fishing.
e Given the offshore distribution of Sandbar Shark, near-shore catches are likely to be negligible.
Commercial catch of Sandbar Shark
Effects of fishing on the marine environment
- Recent analysis of potential changes in ecosystem structure of finfish in the South and West Coast Bioregions of Western Australia14 found no evidence of any systematic change in species diversity or richness, or trophic index, indicating that this fishery is not having a material impact on the food chain or trophic structure.
- The demersal gillnets used to catch Sandbar Shark in Western Australia are deployed infrequently over a small proportion of the target fisheries’ operational area. Under normal circumstances, the physical impact of the gear on the bottom is minimal3.
- Demersal gillnets are known to interact with a number of threatened and protected species in areas where they are used to catch Sandbar Shark. However, such interactions occur at a very low frequency, and have been assessed as posing low to negligible risks to these populations4.
Environmental effects on Sandbar Shark
- Climate change and climate variability have the potential to impact fish stocks in a range of ways, including influencing their geographic distribution (for example, latitudinal shifts in distribution). However, the impact of environmental changes on Sandbar Shark stocks is unknown.
- 1 Last, PR and Stevens, JD 2009, Sharks and rays of Australia, 2nd edn, CSIRO Publishing, Collingwood.
- 2 McAuley, RB, Simpfendorfer, CA, Hyndes, GA and Lenanton, RCJ 2007, Distribution and reproductive biology of the Sandbar Shark, Carcharhinus plumbeus, (Nardo, 1827) in Western Australian waters, Marine and Freshwater Research, 58: 116–126.
- 3 Portnoy, DS, McDowell, JR, Heist, EJ, Musick, JA and Graves, JE 2010, World phylogeography and male-mediated gene flow in the Sandbar Shark, Carcharhinus plumbeus, Molecular Ecology, 19: 1994–2010.
- 4 McAuley, R, Braccini, M, Newman, SJ and O’Malley, J 2015, Temperate Demersal Gillnet and Demersal 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.
- 5 McAuley, R and Rowland, F 2012, Northern Shark Fisheries status report, in WJ Fletcher and K Santoro (eds), Status reports of the fisheries and aquatic resources of Western Australia 2011/12, Western Australian Department of Fisheries, Perth, 222–227.
- 6 Marshall L, Giles, J and Johnson, GJ 2016, Catch composition of a traditional Indonesian shark fishery operating in the MOU Box, northwestern Australia: Results of shark fin identification from Operation Snapshot (May 2015), Australian Fisheries Management Authority, Canberra.
- 7 McAuley, R, Lenanton, R, Chidlow, J, Allison, R and Heist, E 2005, Biology and stock assessment of the Thickskin (Sandbar) Shark, Carcharhinus plumbeus, in Western Australia and further refinement of the Dusky Shark, Carcharhinus obscurus, stock assessment, final report to the Fisheries Research and Development Corporation, project 2000/134, Fisheries research report 151, Western Australian Department of Fisheries, Perth.
- 8 McAuley, RB, Simpfendorfer, CA and Hall, NG 2007, A method for evaluating the impacts of fishing mortality and stochastic influences on the demography of two long-lived shark stocks, ICES Journal of Marine Science, 64: 1710–1722.
- 9 Macbeth, WG, Geraghty, PT, Peddemors, VM and Gray, CA 2009, Observer-based study of targeted commercial fishing for large shark species in waters off northern New South Wales, Fisheries final report series 114, Industry and Investment New South Wales, Cronulla.
- 10 Rowling, KA, Hegarty, A and Ives, M 2010, Status of fisheries resources in NSW 2008/09, Industry and Investment New South Wales, Cronulla.
- 11 Geraghty PT, Macbeth, WG, Harry, AV, Bell, JE, Yerman, MN and Williamson, JE 2013, Age and growth parameters for three heavily exploited shark species off temperate eastern Australia, ICES Journal of Marine Science, 71: 559–573.
- 12 McAuley, RB, Simpfendorfer, CA, Hyndes, GA, Allison, RR, Chidlow, JA, Newman, SJ and Lenanton, RCJ 2006, Validated age and growth of the sandbar shark, Carcharhinus plumbeus (Nardo, 1827) in the waters off Western Australia, Environmental Biology of Fishes, 77: 385–400.
- 13 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.
- 14 Hall, NG and Wise, BS 2010, Development of an ecosystem approach to the monitoring and management of Western Australian fisheries, Fisheries research report 215, Western Australian Department of Fisheries, Perth.