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The Bronze Whaler is distributed widely, but patchily, throughout the world's warm temperate (and some tropical) oceans [Last and Stevens 2009]. In Australia, the species occurs around the southern coastline, from approximately Coffs Harbour in NSW (though with some individuals entering QLD waters) to Geraldton in WA. Available evidence supports a single biological stock, which is classified as undefined, in Australian waters.

Photo Credit: Clinton Duffy, FishBase

South Australia approximates the centre of the Australian distribution of the Bronze Whaler (Carcharhinus brachyurus) [Last and Stevens 2009]. The Bronze Whaler is highly mobile, seasonally migratory and has a cosmopolitan warm-temperate distribution [Last and Stevens 2009]. Adult and juvenile sharks inhabit coastal and shelf waters of the west, south and north coasts of Australia between approximately Coffs Harbour in New South Wales (though with some sharks entering Queensland waters) and Geraldton in Western Australia. Information on the genetic structure of the population suggests that the Indian Ocean is a geographical barrier to gene flow between Australia and South Africa [Benavides et al. 2011]. Within Australian waters, genetic analyses indicate there is a well-mixed stock ranging between western, southern and eastern Australia. Analyses using single-nucleotide polymorphisms (SNPs) provided some support for a potential separation of Western Australia from the rest of Australia and New Zealand (based on neutral loci only), however, this was only based on two (Augusta, Western Australia) of 103 samples [Junge et al. 2019], and hence, should be treated cautiously. Movement processes underlying the preliminary stock structure hypothesis (panmixia) have been studied using telemetry techniques at a range of spatial and temporal scales. The South Australian gulfs form important seasonal foraging habitats in spring-summer [Rogers et al. 2012], with juveniles and adults [Rogers et al. 2013; Drew et al. 2019] moving out of both Spencer Gulf [Rogers and Drew 2018] and Gulf St Vincent during autumn [Drew et al. 2017]. Long-distance migrations were documented between South Australia and Western Australia [SARDI unpublished data, WA DPIRD unpublished data], and southern and eastern Victoria [Rogers et al. 2013]. Movement data collected in Western Australian waters indicates strong seasonality in the species' presence in that jurisdiction, and,  for some individuals, residency between July and January [McAuley et al. 2016]. Evidence supporting seasonal use of Western Australian waters includes detections there of some sharks originally tagged in South Australia.

Based on available evidence including seasonal catch and tagging patterns, genetic population structure, and movement patterns determined from conventional and electronic telemetry, Bronze Whaler is assessed here as a single biological stock spanning South Australia, Victoria, New South Wales, southern Queensland at the species range limits, and WA. Additionally, Bronze Whaler inhabits Commonwealth waters adjacent to these jurisdictions). 

Southern Australia

Most of the undifferentiated whaler shark catch is harvested in South Australia by fishers in the commercial multi-species, multi-gear and multi-sectoral Marine Scalefish Fishery (MSF) [Steer et al. 2020]. The main gear-type used is longlines (77 per cent), although other gear types including droplines and handlines are also used. Fishery logbook data do not resolve catches of Bronze Whaler and Dusky Shark to the level of species. This lack of resolution at the species level is the main source of uncertainty hampering formal stock assessment for Bronze Whaler [Steer et al. 2020]. Short-term, onboard fishery sampling programs found the mixed whaler shark catches in the MSF were predominantly comprised of Bronze Whalers (80‒96 per cent), with Dusky Shark making up the remainder of observed catches [Rogers et al. 2013; Drew et al. 2017]. Annual total catches range from 45 to 155 t, with an average of 82 t/year between 1999–00 and 2018–19. 

Information on the recreational take of whaler sharks (assumed to be mostly Bronze Whaler) is limited to nominal catch data. On average, 723 whaler sharks were taken per year during the most recent survey (conducted during 2013–14), all of which were released [Giri and Hall 2015]. The South Australian Charter Boat Fishery reported harvesting <40 whaler sharks per year for an overall total of 194 between 2007–08 and 2018–19. There were no data available on the Indigenous catch, although anecdotal evidence suggests small numbers are taken annually from the shore for subsistence purposes.

Among Commonwealth fisheries, Bronze Whalers are predominately taken in sectors of the Southern and Eastern Scalefish and Shark Fishery (SESSF), with catch also reported in the Eastern Tuna and Billfish Fishery (ETBF) and the Western Tuna and Billfish Fishery (WTBF). Average annual catches for the combined Commonwealth fisheries are <30 t per year. Overall, these low catch levels constitute a relatively small proportion of the total annual catch taken from the Southern Australia stock.

In WA, Bronze Whalers are predominately taken in the Temperate Demersal Gillnet and Demersal Longline Fisheries. The main shark species captured in these fisheries are Gummy Shark, Dusky Shark, Whiskery Shark and Sandbar Sharks. Bronze Whalers constitute only a minor component of the catch. Species-specific records of Bronze Whaler are available since 1998, averaging 40 t per year for the last 10 years. The recreational catch level is negligible [Ryan et al 2019]. 

Bronze Whaler catches in New South Wales fisheries have consistently been below 22 t since 2009 when new species-specific logbook reporting was initiated. During the past six years, the catch has been <16 t, with the reported catch for 2019–20 being 13 t. The recreational catch is negligible [Murphy et al 2020]. There is no knowledge on levels of Indigenous harvest, however it is also likely to be negligible. Overall, these low catch levels constitute a small proportion of the total annual catch taken from the broader Southern Australia stock.

In Queensland, the Bronze Whaler is at the north-eastern end of its distribution, with catches occurring from Moreton Bay to the New South Wales border. The reported commercial harvest of Bronze Whalers taken by Queensland-managed fisheries averaged less than 300 kg per year since 1996, with no harvest reported for eight of those years [QFISH 2020]. There are no reliable reports of recreational catch of Bronze Whaler in Queensland although with current management restrictions, harvest levels are assumed to be small. Overall, these low catch levels constitute a negligible proportion of the total annual catch taken from the Southern Australia stock.

Victoria’s low catch levels constitute a very small proportion of the total annual catch (0.5 per cent of national landings during the past decade) taken from the stock. The catch taken by Victorian-managed fisheries over the past two decades has totalled 14 t. At least one third of the catch is taken as by-catch.

There is no published stock assessment for the Southern Australia Bronze Whaler stock. In South Australia, population productivity and susceptibility to different harvest fractions was determined by Bradshaw et al. (2018) using Leslie matrix models. However, these models do not include catches from all sectors or jurisdictions, nor do they provide enough information to estimate biomass or exploitation rates. In addition, there is no knowledge of recruitment. This prevents assessment of current stock size or fishing pressure. Consequently, there is insufficient information available to confidently classify the status of this stock.

On the basis of the evidence provided above, the Southern Australia biological stock is classified as an undefined stock. 

Bronze Whaler biology [Drew et al. 2017]

Distribution of reported commercial catch of Bronze Whaler

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.

Commercial catch of Bronze Whaler - note confidential catch not shown

1. Benavides, M. T., Feldheim, K. A., Duffy, C. A., Wintner, S., Braccini, J. M., Boomer, J., Huveneers, C., Rogers, P., Mangel, J. C., Alfaro, Shigueto, J., Cartamil, D. P., and Chapman, D. D. 2011, Phylogeography of the copper shark (Carcharhinus brachyurus) in the southern hemisphere: implications for the conservation of a coastal apex predator. Marine and Freshwater Research 62(7), 861–869. doi:10.1071/MF10236
2. Bradshaw CJ, Prowse TA, Drew M, Gillanders BM, Donnellan SC, Huveneers C, Kuparinen A 2018, Predicting sustainable shark harvests when stock assessments are lacking. ICES J Mar Sci 75(5):1591–1601
3. Cappo, M 1992, Bronze whaler sharks in South Australia. SA Fisheries 15]17, 10–12.
4. Cheung, W. W. L., Pitcher, T. J., and Pauly, D. 2007, Intrinsic vulnerability in the global fish catch. Marine Ecology Progress Series 333, 1–12. doi:10.3354/MEPS333001
5. Cliff, G., and Dudley, S. F. J. 1992, Sharks caught in the protective gillnets off Natal, South Africa. 6. The copper shark Carcharhinus brachyurus (Gunther). South African Journal of Marine Science 12, 663–674. doi:10.2989/02577619209504731
6. Drew M, Rogers, P, Huveneers C. 2017, Slow life-history traits of a neritic predator, the bronze whaler (Carcharhinus brachyurus). Mar Freshw Res 68:461–472
7. Drew, M, Rogers, P, Lloyd, M, Huveneers, C 2019, Seasonal occurrence and site fidelity of juvenile bronze whalers (Carcharhinus brachyurus) in a temperate inverse estuary.
8. Dudley, S.FJ and Simpfendorfer, CA 2006, Population status of 14 shark species caught in the protective gillnets off KwaZulu-Natal beaches, South Africa, 1978–2003. Marine and Freshwater Research 57, 225–240. doi:10.1071/MF05156Lucifora et al. 2005, 2009
9. Fowler, AJ, Rogers, PJ, Smart, J 2020, South Australian Research and Development Institute (Aquatic Sciences) ESD risk assessment for ‘lesser known’ species to facilitate structural reform of South Australia’s Marine Scalefish Fishery. Adelaide, August.
10. Giri, K and Hall, K 2015, South Australian Recreational Fishing Survey. Fisheries Victoria Internal Report Series No. 62.
11. Henry G, Lyle J, 2003, The National Recreational and Indigenous Fishing Survey. FRDC Project No. 99/158. New South Wales Fisheries.
12. Jones G. K 2008, Review of the fishery status for whaler sharks (Carcharhinus spp.). In: South Australian and adjacent waters. SARDI Aquatic Sciences report, Adelaide, Australia
13. Jones G. K 2008, Review of the fishery status for whaler sharks (Carcharhinus spp.). In: South Australian and adjacent waters. SARDI Aquatic Sciences report, Adelaide, Australia
14. Junge, C, Donnellan, SC, Huveneers, C, Gillanders, BM, Rogers, PJ 2019, Comparative population genomics confirms little population structure in two commercially targeted carcharhinid sharks. Marine Biology 166 (2) DOI: 10.1007/s00227-018-3454-4.
15. Junge, C, Donnellan, SC, Huveneers, C, Gillanders, BM, Rogers, PJ 2019, Comparative population genomics confirms little population structure in two commercially targeted carcharhinid sharks. Marine Biology 166 (2) DOI: 10.1007/s00227-018-3454-4.
16. Last PR, Stevens, JD 2009, ‘Sharks and Rays of Australia.’ 2nd edn. (CSIRO Publishing: Melbourne).
17. Last, PR, Stevens, JD 2009, ‘Sharks and Rays of Australia.’ 2nd edn. (CSIRO Publishing: Melbourne).
18. Lucifora, LO, Garcia, VB, Menni, RC, Escalante, AH, Hozbor, NM, 2009, Effects of body size, age and maturity stage on diet in a large shark: ecological and applied implications. Ecological Research 24, 109–118. doi:10.1007/S11284-008-0487-Z.
19. Lucifora, LO, Menni, RC, Escalante, AH 2005, Reproduction and seasonal occurrence of the copper shark, Carcharhinus brachyurus, from north Patagonia, Argentina. ICES Journal of Marine Science 62, 107–115. doi:10.1016/J.ICESJMS.2004.09.003
20. McAuley, R, Bruce, B, Keay, I, Mountford, S, Pinnella, T, 2016, Evaluation of passive acoustic telemetry approaches for monitoring and mitigating shark hazards off the coast of Western Australia. Fisheries Research Report No. 273, Department of Fisheries, Western Australia. 84pp.
21. Murphy, J.J, Ochwada-Doyle, FA, West, LD, Stark, KE, Hughes, JM, 2020, The NSW Recreational Fisheries Monitoring Program - survey of recreational fishing, 2017/18. NSW DPI - Fisheries Final Report Series No. 158.
22. QFish, Department of Agriculture and Fisheries, www.qfish.gov.au
23. Rogers P, Huveneers C, Goldsworthy S, Cheung W, Jones G, Mitchell J 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. Mar Freshw Res 64:20–30
24. Rogers PJ, Huveneers C, Page B, Hamer DJ, Goldsworthy SD, Mitchell JG, Seuront L, 2012, A quantitative comparison of the diets of sympatric pelagic sharks in gulf and shelf ecosystems off southern Australia. ICES J Mar Sci (Journal du Conseil) 69:1382–1393
25. Rogers, PJ, Drew, MD, 2018, Application of tracking technologies to understand patterns of movement, residency and habitat use of pelagic sharks in Spencer Gulf: resolving overlaps with community activities and marine industries. FRDC Final Report Project 2014/020). 104pp.
26. 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, Western Australia.
27. Smale, MJ, 1991, Occurrence and feeding of three shark species, Charcharhinus brachyurus, C. obscurus and Sphyrna zygaena, on the Eastern Cape Coast of South Africa. South African Journal of Marine Science 11, 31–42. doi:10.2989/025776191784287808.
28. South Australian Charter Boat Fishery Data Summary. Final Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2011/000438-3. SARDI Research Report Series No. 1070. 19 pp.
29. Steer, MA., Fowler, T, Rogers, P.J, Bailleul, F, Earl, J, Matthews, D, Drew, M, Tsolos, A 2020, Assessment of the South Australian Marine Scalefish Fishery in 2018. Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2017/000427-3. SARDI Research Report Series No. 1049. 213 pp.
30. Walter, JP, Ebert, DA, 1991, Preliminary estimates of age of the bronze whaler Carcharhinus brachyurus (Chondrichthyes: Carcharhinidae) from Southern Africa, with a review of some life history parameters. South African Journal of Marine Science 10, 37–44. doi:10.2989/02577619109504617