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Dusky Whaler is a common, large-bodied whaler shark shark found throughout tropical and temperate waters of Australia.  In Western Australia stocks are recovering and there is a sustainable stock in eastern Australia.

Dusky Whaler has a tropical to warm-temperate distribution and is found off the west, south and north coasts of Australia, mostly between latitudes 18°S and 36°S [McAuley et al. 2007; Rogers et al. 2013a], and off the east coast, where the full extent of the species' geographic distribution is unclear. Electronic and conventional tagging studies have shown Dusky Whalers move between South Australia and Western Australia [Simpfendorfer et al. 1999; Rogers et al. 2013b; Huveneers et al. 2014, 2021] and between Queensland, New South Wales, Victoria and Tasmania [Huveneers et al. 2021], and genetic analyses suggest there is restricted gene flow between Dusky Whaler off eastern and western Australia [Geraghty et al. 2014]. Therefore, Dusky Whaler in South Australian, Western Australian and Northern Territory  waters are considered to form a single biological stock (the Western Australia stock). This biological stock exhibits a high degree of ontogenetic segregation, with juveniles most common in temperate latitudes and adults in warmer northern latitudes [McAuley et al. 2007, 2015].

Here, assessment of stock status is presented at the biological stock level—western Australia and eastern Australia.

Eastern Australia

Dusky Whaler is taken as a non-target species by Commonwealth fishers in the Eastern Tuna and Billfish Fishery (ETBF). The species has been considered using ecological risk assessment methods and found to be at medium risk [Sporcic et al. 2019]. Commonwealth commercial catch averaged less than one tonne (t) per year during the 2017–18 to 2021–22 financial years and was less than 1 t in the 2021–22 financial year. 

 In Queensland, species-specific reporting for the Dusky Whaler commenced in 2009 and is now required in all fisheries that retain shark. However, the species is only retained in small quantities in the East Coast Inshore Fishery (ECIF). Annual harvest rates since 2008–09 range from 0.4 t to 3.7 t with the ECIF retaining an annual average of 1.4 t of Dusky Whaler over the last 10 years (2012–13 to 2021–22). This average declines to  0.8 t when only the last five years of data are considered (2016–17 to 2021–22).

Outside of the commercial fishing sector, the catch of Dusky Whaler in Queensland waters is low to negligible. On average, 11 Dusky Whalers are caught in the Queensland Shark Control Program each year (2001–2017 data) [Queensland Government, 2023]. No recreational data is available for this species [Teixeira et al. 2021]. However, recreational harvest is limited by a one shark in possession limit and a maximum legal size limit of 1.5 m total length. 

 In New South Wales, Dusky Whaler was not identified and reported at the species level in commercial catch logbooks until 2009. Observer data indicate that whaler sharks are the second most commonly caught shark species group in the New South Wales Ocean Trap and Line Fishery (15% of overall catch) [Macbeth at al. 2009]. Historical catch of Dusky Whaler is therefore likely to have been around 7.5 t from 2000 to 2005, whereafter increased targeting of large whaler sharks led to three years of higher catch, peaking at approximately 30 t in 2006–07. Dusky Whaler catch reduced to approximately15 t in 2007–08 once fishers started differentiating some of the whaler sharks in preparation of the new species-specific logbook requirements, specific conditions and restrictions being implemented in the OTL fishery [Macbeth et al. 2009]. Since 2015, under 3 t of Dusky Whaler was landed each year by the OTL fishery in New South Wales. An annual catch of less than one t was reported by the New South Wales Shark Meshing Program.  

Application of a new software package known as NeOGen [Blower et al 2019] estimated the total population size of Dusky Whalers on the eastern Australian coastline at approximately 35,000 individuals [Blower 2020].  Simulations at the historically higher fishing levels indicate those fishery harvest volumes to be sustainable [Blower 2020; Peddemors et al. 2020].

The above evidence indicates that the biomass of this stock is unlikely to be depleted and recruitment is unlikely to be impaired. The above evidence also indicates that 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 Eastern Australia biological stock is classified as a sustainable stock.

Dusky Whaler biology [Simpfendorfer et al. 2002; McAuley et al. 2007; Geraghty et al. 2013, 2016; Kyne et al. 2021]

Distribution of reported commercial catch of Dusky Whaler

Commercial (catch) Western Australian (state) and Eastern Australia biological stock is for Dusky Whaler only. However, South Australian catches are reported as undifferentiated whaler sharks and are therefore not presented.

Commonwealth – Commercial Data provided for the Commonwealth align with 2021–22 financial year.

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.

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.

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

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.”

Queensland – Commercial QLD commercial and charter data has been sourced from the commercial fisheries logbook program.  Further information available through the Fisheries Summary Report (https://www.daf.qld.gov.au/business-priorities/fisheries/monitoring-research/data/queensland-fisheries-summary-report)  

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

Commercial catches of Dusky Whaler - note confidential catch not shown

1. Blower DC, Riginos, C and Ovenden, JR. 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. 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(7), 1337-1350
5. Continental-Scale Network Reveals Cross-Jurisdictional Movements of Sympatric Sharks With Implications for Assessment and Management. Frontiers in Marine Science 8: 697175
6. Geraghty PT, Macbeth WG and Williamson JE 2016, Aspects of the reproductive biology of dusky, spinner and sandbar sharks (Family Carcharhinidae) from the Tasman Sea, Marine and Freshwater Research, 67: 513–525
7. 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.
8. Geraghty, PT, Williamson, JE, Macbeth, WG, Blower, DC, Morgan, JAT, Johnson, G, Ovenden, JR and Gillings, MR 2014, Genetic structure and diversity of two highly vulnerable carcharhinids in Australian waters, Endangered Species Research, 24: 45–60.
9. Huveneers, C, Rogers, P and Drew, M 2014, Monitoring shark species of conservation concern within the Adelaide metropolitan and Gulf St Vincent regions, final report to the Adelaide and Mount Lofty Ranges Natural Resources Management Board, South Australian Research and Development Institute (Aquatic Sciences), SARDI publication F2013/000716-1, SARDI research report series 754, SARDI, Adelaide, 89.
10. JABBA: Just Another Bayesian Biomass Assessment. Fish. Res. 204, 275–288
11. Jones, K 2008, Review of the fishery status for whaler sharks (Carcharhinus spp.) in South Australian and adjacent waters, report to the Fisheries Research and Development Corporation, FRDC project 2004/067, South Australian Research and Development Institute (Aquatic Sciences) publication F2007/000721-1, SARDI research report series 154, SARDI, Adelaide.
12. Kyne, P. M., Heupel, M. R., White, W. T. & Simpfendorfer, C. A. (2021). The Action Plan for Australian Sharks and Rays 2021. National Environmental Science Program. Hobart, Australia.
13. 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, Cronulla Fisheries Research Centre of Excellence, New South Wales Industry and Investment, Cronulla.
14. 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), 2016/001375, Australian Fisheries Management Authority, Canberra.
15. McAuley, R and Simpfendorfer, C 2003, Catch composition of the Western Australian Temperate Demersal Gillnet and Demersal Longline fisheries, 1994–1999, Fisheries research report 146, Western Australian Department of Fisheries, Perth.
16. 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.
17. 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.
18. Peddemors, V, Macbeth, W, Collins, D, Goulstone, A, Ives, M., Ovenden, J., Butcher, P. 2020. Shark Futures: Sustainable management of the NSW whaler shark fishery. Port Stephens, NSW. 190pp
19. 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).
20. Rogers, P, Huveneers, C, Goldsworthy, SD, Mitchell, JG and Seuront, L 2013, Broad-scale movements and pelagic habitat of the Dusky Shark Carcharhinus obscurus off Southern Australia determined using pop-up satellite archival tags, Fisheries and Oceanography, 22: 102–112.
21. Rogers, PR, Huveneers, C, Goldsworthy SD, Cheung, WWL, Jones KG, Mitchell, JG and Seuront, L 2013, Population metrics and movement of two sympatric carcharhinids: a comparison of the vulnerability of pelagic sharks of the southern Australian gulfs and shelves, Marine and Freshwater Research, 64: 20–30.
22. Simpfendorfer CA, McAuley R, Chidlow JA, Lenanton R, Hall N and Bastow T 1999. Biology and stock assessment of Western Australia’s commercially important shark species. Project 96/130 Fisheries Research and Development Corporation, Department of Fisheries of Western Australia, Perth.
23. Simpfendorfer, C 1999, Demographic analysis of the dusky shark fishery in southwestern Australia, in JA Musick (ed.), Life in the slow lane: Ecology and conservation of long-lived marine animals, American Fisheries Society Symposium 23, Bethesda, Maryland, 149–160.
24. Simpfendorfer, CA, McAuley, R, Chidlow, J and Unsworth, P 2002, Validated age and growth of the Dusky Shark, Carcharhinus obscurus, from Western Australian waters, Marine and Freshwater Research, 53: 567–573.
25. Sporcic, M, Hobday, A, Bulman, C, Hartog, J, Fuller, M 2019 Ecological Risk Assessment for the Effects of Fishing: Report for the Eastern Tuna and Billfish Fishery: Longline sub-fishery, data to 2015. Report for the Australian Fisheries Management Authority. 234 pp.
26. Stock synthesis: A biological and statistical framework for fish stock assessment and fishery management. Fish. Res. 142, 86–99
27. Teixeira, D, Janes, R, and Webley, J 2021, 2019–20 Statewide Recreational Fishing Survey Key Results. Project Report. State of Queensland, Brisbane.