*

Common Blacktip Sharks are found worldwide in tropical and warm temperate waters. Three biological stocks—East Coast, Gulf of Carpentaria and North and West Coast—have been identified for Australia. The East Coast and North and West Coast stocks are sustainable, while the Gulf of Carpentaria stock is undefined. Previous editions of the SAFS reports have combined Australian Blacktip Shark, Common Blacktip Shark and Spot-Tail Shark, but all three are now reported at the species level.

Photo: Department of Industry, Tourism and Trade, Northern Territory

Common Blacktip Shark have a circumglobal distribution in tropical and warm temperate waters. In Australian waters, genetic studies have identified three biological stocks of Common Blacktip Shark; a western stock extending from the western Northern Territory into northern Western Australia, a Gulf of Carpentaria (GoC) stock and an east coast stock in Queensland and New South Wales [Ovenden et al. 2007]. The stock boundary between the North and West Coast, and Gulf of Carpentaria biological stocks is uncertain. 

Common Blacktip Shark are similar in appearance to the Australian Blacktip Shark (C. tilstoni). Previously taxonomical differentiation of these species was only possible by genetic analyses, precaudal vertebral counts or, in certain size classes, differences in size of maturity [Harry 2011]. A new identification technique, utilising body measurements and pelvic fin colouration, has been developed and may assist in distinguishing between these two species. However, accurate field identification remains difficult and is not practical during commercial fishing operations [Johnson et al. 2017]. Hybridisation between the species has also been recorded and, while a new investigation is helping to understand the prevalence and dynamics of this phenomenon [Queensland Department of Agriculture and Fisheries 2021], the current knowledge regarding its implications for fisheries assessment and management is limited [Harry et al. 2012; Johnson et al. 2017; Morgan et al. 2011]. Consequently, Common Blacktip and Australian Blacktip sharks are often reported as a species complex in commercial logbooks.  For the purpose of these assessments a portion of the combined Blacktip Shark catch for each jurisdiction has been attributed to Common Blacktip Shark using relative abundance ratios determined from on board observer programs and published research [Johnson et al. 2017; Ovenden 2007].

Here, assessment of stock status for Common Blacktip Shark is presented at the biological stock level—North and West Coast, Gulf of Carpentaria, and East Coast.

North Western Australia

The North Western Australia biological stock straddles two jurisdictions: The Northern Territory, west of the Wessel Islands–Western Australian border; and Western Australia.

Changing operational practices in the NT Offshore Net and Line Fishery have greatly reduced the take of Common Blacktip Shark in the Northern Territory. There has been little to no shark-targeted fishing occurring in the Northern Territory since 2012. This is attributed to declining shark fin prices and increasing value of Grey Mackerel (Scomberomorus semifasciatus), which is currently the main target species of this fishery. In this circumstance, the declining catches are likely to have allowed the abundance of the population of Common Blacktip Shark to increase.

Although there is uncertainty regarding species composition and the magnitude of historical catches of Blacktip Sharks from Western Australia, harvests of Common Blacktip Shark in this jurisdiction have been negligible since April 2009 [Molony et al. 2013; Braccini et al. 2021]. These negligible harvests are expected to allow for increasing biomass levels. In addition, recreational catches are negligible [Ryan et al. 2019].

The most recent stock assessment, using data up to 2021, was undertaken for the North Western Australia biological stock of Common Blacktip Shark utilising a catch-MSY model (developed by Martell and Froese [2013] and modified by Haddon et al. [2018]). The results indicate that the inferred biomass exceeds the target reference point, with the 95% confidence intervals positioned above the target. This indicates that the stock is unlikely to be depleted and that recruitment is unlikely to be impaired. The assessment also estimated that recent harvests are below that required to achieve maximum sustainable yield [Northern Territory Government, unpublished]. The biomass of the stock is not considered to be depleted and 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 North Western Australia biological stock of Common Blacktip Shark is classified as a sustainable stock.

Blacktip Sharks biology [Harry 2011; Harry et al. 2019; Last and Stevens 2009]

Distribution of reported commercial catch of Common Blacktip Shark

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 informationsee https://www.daf.qld.gov.au/business-priorities/fisheries/traditional-fishing

Queensland – Commercial (Catch). Queensland commercial and charter data have been sourced from the commercial fisheries logbook program. Due to low confidence in species-specific reporting caused by challenges in distinguishing between C. limbatus and C. tilstoni, catch for this species has been derived by combining harvest across the multiple blacktip shark reporting categories and applying a latitudinal split following Leigh [2015] and Ovenden et al. [2007]. Further information available through the Queensland Fisheries Summary Report https://www.daf.qld.gov.au/business-priorities/fisheries/monitoring-research/data/queensland-fisheries-summary-report

Queensland – Recreational Fishing (Catch). Data with high uncertainty (Residual Error >50 %) has been excluded and listed as unknown. More information available at: https://www.daf.qld.gov.au/business-priorities/fisheries/monitoring-research/monitoring-reporting/statewide-recreational-fishing-surveys  

Queensland – Indigenous (management methods). For more informationsee https://www.daf.qld.gov.au/business-priorities/fisheries/traditional-fishing

Queensland – Commercial (Management Methods). Harvest strategies are available at: https://www.daf.qld.gov.au/business-priorities/fisheries/sustainable/harvest-strategy  

New South Wales – Indigenous (Management Methods). https://www.dpi.nsw.gov.au/fishing/aboriginal-fishing

Northern Territory - Indigenous (management methods). The Fisheries Act 1988 (NT), specifies that: “Unless expressly provided otherwise, nothing in this Act derogates or limits the right of Aboriginal people who have traditionally used the resources of an area of land or water in a traditional manner to continue to use those resources in that area in that manner.”

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.

Commercial catch of Common Blacktip Shark - note confidential catch not shown

1. Braccini, M, Kangas, M, Jaiteh, V and Newman, S 2021, Quantifying the unreported and unaccounted domestic and foreign commercial catch of sharks and rays in Western Australia. Ambio 50: 1337-1350
2. Dalton, S, Peddemors, V and Doak, C 2023, Shark Mehsing (Bather Protection) Program 2022/23 Annual Performance Report. NSW Department of Primary Industries. 45 pp.
3. Department of Agriculture and Fisheries, Queensland 2021, Monitoring of Queensland’s shark catch for the net fisheries: summary report. Project Report. State of Queensland, Brisbane.
4. 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.
5. Harry, AV 2011, Life histories of commercially important tropical sharks from the Great Barrier Reef World Heritage Area, PhD thesis, James Cook University, Townsville
6. Harry, AV, Butcher, PA, Macbeth, WG, Morgan, JAT, Taylor, SM and Geraghty, PT 2019, Life history of the Common Blacktip Shark, Carcharhinus limbatus, from central eastern Australia and comparative demography of a cryptic shark complex. Marine and Freshwater Research, 70, 6, 834-848
7. Harry, AV, Morgan, JAT, Ovenden, JR, Tobin, A, Welch, DJ and Simpfendorfer, C 2012, Comparison of the reproductive ecology of two sympatric Blacktip Sharks (Carcharhinus limbatus and Carcharhinus tilstoni) off north-eastern Australia with species identification inferred from vertebral counts. Journal of Fish Biology, 81: 1225–1233.
8. Johnson, GJ, Buckworth, RC, Lee, H, Morgan, JAT, Ovenden, JR and McMahon, CR 2017, A novel field method to distinguish between cryptic carcharhinid sharks, Australian blacktip shark Carcharhinus tilstoni and common blacktip shark C. limbatus, despite the presence of hybrids. Journal of Fish Biology, 90, 1, 39-60.
9. Last, PR and Stevens, JD 2009, Sharks and rays of Australia, CSIRO Publishing, Collingwood.
10. Leigh GM 2015, Stock assessment of whaler and hammerhead sharks (Carcharhinidae and Sphyrinidae) in Queensland, Agri-Science Queensland, Department of Agriculture and Fisheries, Brisbane.
11. 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 fishery. Fisheries Management and Ecology, 25: 186-202.
12. Macbeth, WG, Geraghty, PT, Peddemors, VM, and Gray, CA 2009, Observer-based study of targeted commercial fishing for large shark species in waters of New South Wales, Industry and Investment New South Wales. Fisheries Final Report Series 82.
13. Martell, S, and Froese, R 2013, A simple method for estimating MSY from catch and resilience. Fish and Fisheries 14:504–514.
14. Molony, B, McAuley, R and Rowland, F 2013, Northern shark fisheries status report: Statistics only, in WJ Fletcher and K Santoro (eds), Status Reports of the Fisheries and Aquatic Resources of Western Australia 2012/13: The State of the Fisheries, Western Australian Department of Fisheries, Perth, 216–217.
15. Morgan, JA, Harry, AV, Welch, DJ, Street, R, White, J, Geraghty, PT, Macbeth, WG, Tobin, A, Simpfendorfer, CA and Ovenden, JR 2011, Detection of interspecies hybridisation in Chondrichthyes: hybrids and hybrid offspring between Australian (Carcharhinus tilstoni) and common (C. limbatus) Blacktip Shark found in an Australian fishery. Conservation Genetics, 13: 455–463.
16. Ovenden, JR, Street, R, Broderick, D, Kashiwagi, T and Salini, J 2007, Genetic population structure of Black-tip Sharks (Carcharhinus tilstoni and C. sorrah) in northern Australia, in J Salini, R McAuley, S Blaber, RC Buckworth, J Chidlow, N Gribble, JR Ovenden, S Peverell, R Pillans, JD Stevens, I Stobutzki, C Tarca and TI Walker (eds), Northern Australian sharks and rays: the sustainability of target and bycatch species, phase 2, Fisheries Research and Development Corporation, Cleveland, Queensland.
17. Queensland Fisheries Harvest Strategies. Available at: https://www.daf.qld.gov.au/business-priorities/fisheries/sustainable/harvest-strategy (Accessed 18 October 2023).
18. Queensland Government, 2023, Shark Control Program: Shark Catch Statistics by Year. Available at: https://www.data.qld.gov.au/dataset/shark-control-program-shark-catch-statistics (Accessed: 2 August 2023).
19. 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, Government of Western Australia, Perth.
20. Stock Status Summary - 2022 Common Blacktip Shark (Carcharhinus limbatus) North and West Coast stock Catch-MSY. Unpublished Fishery Report
21. Teixeira, D, Janes, R, and Webley, J 2021, 2019–20 Statewide Recreational Fishing Survey Key Results. Project Report. State of Queensland, Brisbane.
22. Usher, M, Saunders, T and Roelofs, A 2020a, Stock Status Summary - 2020 Common Blacktip Shark (Carcharhinus limbatus) East Coast stock Catch-MSY. Unpublished Fishery Report