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Sandbar Shark (2020)

Carcharhinus plumbeus

  • Matias Braccini (Department of Primary Industries and Regional Development, Western Australia)
  • Alice Pidd (Department of Agriculture and Fisheries, Queensland)
  • Michael Usher (Department of Primary Industry and Resources, Northern Territory)
  • Victor Peddemors (Department of Primary Industries, New South Wales)

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Summary

Sandbar Shark occurs primarily off both the east and west coasts of Australia. The eastern Australian stock is sustainable and the Western Australian stock is recovering.

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Stock Status Overview

Stock status determination
Jurisdiction Stock Stock status Indicators
Northern Territory Western Australia Recovering Catch, CPUE , fishing mortality
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Stock Structure

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 coast [McAuley et al. 2007, Last and Stevens 2009]. 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 stocks [Portnoy et al. 2010], 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 Australia and Eastern Australia.

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Stock Status

Western Australia

In Western Australia, Sandbar Shark is targeted by the West Coast Demersal Gillnet and Demersal Longline Fishery, and is also taken in lesser quantities by the Joint Authority Southern Demersal Gillnet and Demersal Longline Managed Fishery [McAuley et al. 2015]. Sandbar Shark was also previously targeted by the Western Australian North Coast Shark Fishery [McAuley and Rowland 2012]. The Western Australia 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 Australia biological stock, as is an unquantified catch from the Memorandum of Understanding (Mou) Box Shark Fishery [Marshall et al. 2016]. Neither the historical Northern Territory catches nor those from the MoU Box Shark Fishery are explicitly included in assessments of the Western Australian 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 techniques [McAuley et al. 2005, McAuley et al. 2007]. In addition, a risk-based weight of evidence (WoE) approach has been adopted using all available lines of evidence, including simulated biomass trajectories derived from a combination of demographic modelling and catch-only stock reduction analysis [Braccini et al. 2018]. 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 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 2005 [McAuley and Rowland 2012, McAuley et al. 2005].

Since 2010, Sandbar Shark catches have remained well below the levels that will allow a gradual recovery of the breeding stock [McAuley et al. 2015]. 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 stock [McAuley et al. 2015].

The recent WoE assessment estimated a “Medium” current risk level for the Sandbar Shark stock, with 62 per cent, 83 per cent and 99 per cent of the simulated current (2015–16) relative total biomass trajectories being above the target, threshold and limit biomass reference points, respectively, and biomass projections indicating continued stock rebuilding under current fishing and management settings [Braccini et al. 2018].

The above evidence indicates that the biomass of this stock is likely to be depleted and that recruitment is likely to have been impaired. However, available indicators suggest a recovering stock. The current level of fishing mortality should allow the stock to recover from its recruitment impaired state.

On the basis of the evidence provided above, the Western Australia biological stock is classified as a recovering stock.

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Biology

Sandbar Shark biology [Geraghty et al. 2013, McAuley et al. 2007, McAuley et al. 2006]

Biology
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
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Distributions

Distribution of reported commercial catch of Sandbar Shark

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Tables

Fishing methods
Northern Territory
Commercial
Gillnet
Recreational
Hook and Line
Management methods
Method Northern Territory
Commercial
Gear restrictions
Processing restrictions
Quota
Spatial closures
Vessel restrictions
Recreational
Gear restrictions
Possession limit
Catch
Northern Territory
Commercial 42.00kg
Indigenous Unknown but likely to be negligible
Recreational Unknown but likely to be negligible

Western Australia – Recreational (Management methods) A recreational fishing from boat licence is required for recreational fishing from a powered vessel in Western Australia.

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 commercial fisheries with less than seven active fishers are not presented due to the Privacy Act.

Recreational and Indigenous (catch) Given the offshore distribution of Sandbar Shark, near-shore catches are likely to be negligible.

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Catch Chart

Commercial catch of Sandbar Shark - note confidential catch not shown
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References

  1. Blower D.C., C. Riginos, J.R. Ovenden. (2019). NeOGen: A tool to predict genetic effective population size (Ne) for species with generational overlap and to assist empirical Ne study design. Molecular Ecology Resources 19: 290-271.
  2. Blower, D. C. 2020. Estimating contemporary abundance, demography, and vulnerability to change for long-lived species with effective population size and population simulation. PhD thesis. School of Biological Sciences, p. 257. The University of Queensland.
  3. Braccini, M, Blay, N, Hesp, A, and Molony, B 2018. Resource Assessment Report Temperate Demersal Elasmobranch Resource of Western Australia. Department of Primary Industries and Regional Development. Fisheries Research Report No. 294 Department of Primary Industries and Regional Development, Western Australia. 149 pp
  4. 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.
  5. Last, PR and Stevens, JD 2009, Sharks and rays of Australia, 2nd edn, CSIRO Publishing, Collingwood.
  6. Macbeth, WG, Butcher, PA, Collins, D, McGrath, SP, Provost, SC, Bowling, AC, Geraghty, PT and Peddemors, VM 2018, Improving reliability of species identification and logbook catch reporting by commercial fishers in an Australian demersal shark longline. Fisheries Management and Ecology, 25: 186–202.
  7. 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.
  8. 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.
  9. 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.
  10. 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.
  11. 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.
  12. 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.
  13. 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.
  14. 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.
  15. 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.
  16. QFish, Department of Agriculture and Fisheries, www.qfish.gov.au
  17. Rowling, KA, Hegarty, A and Ives, M 2010, Status of fisheries resources in NSW 2008/09, Industry and Investment New South Wales, Cronulla.
  18. Ryan, K.L., Hall, N. G., Lai, E. K., Smallwood, C. B., Tate, A., Taylor, S. M. and Wise, B. S. (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

Downloadable reports

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