*

Southern Bluefin Tuna is a highly migratory species that spawns in the north-east Indian Ocean and migrates throughout the temperate regions around Australia. This global stock is classified as sustainable.

Jurisdiction	Stock	Stock status	Indicators
Commonwealth	Global	Sustainable	Spawning stock biomass, projections of rebuilding

Southern Bluefin Tuna constitutes a single, highly migratory biological stock that spawns in the north-east Indian Ocean and migrates throughout the temperate southern oceans, supporting a number of international fisheries [Proctor et al. 1995, Evans et al. 2012, Patterson et al. 2018].
Here, assessment of stock status is presented at the biological stock level—Global. dd

Global

Southern Bluefin Tuna is fished by Australian fishers endorsed to operate in the Southern Bluefin Tuna Fishery (Commonwealth). Fishers in the Eastern Tuna and Billfish Fishery (Commonwealth) and the Western Tuna and Billfish Fishery (Commonwealth) who have quota for Southern Bluefin Tuna can retain catches of the species. The species is also caught by recreational fishers in the waters off southern Australia, with catch estimated to be 270 t in 2018–19 [Tracey et al. 2020].

The most recent stock assessment (2020) undertaken by the CCSBT took into account reported catch from all international jurisdictions [CCSBT 2020, Hillary et al. 2020]. It also examined the sensitivity of the results to alternate scenarios for unaccounted fishing mortalities and other parameters. Since 2009, the stock has been rebuilding by approximately 5% per year and recruitment levels remain above historical averages [CCSBT 2021]. The most recent estimate of total reproductive output of the Southern Bluefin Tuna stock is 20 per cent (80 per cent confidence interval 16-24 per cent) of initial levels [Hillary et al. 2020]. The estimate of fishing mortality in 2019 was 52 per cent (80 per cent confidence interval 37–73 per cent) of the level associated with maximum sustainable yield [Hillary et al. 2020]. All projections undertaken as part of the stock assessment indicate that the adult stock will remain above 20% of initial levels in 2035 with a high probability [Hillary et al. 2020].

On the basis of the evidence provided above, the global biological stock is classified as a sustainable stock

Southern Bluefin Tuna biology [Davis et al. 2001, Laslett et al. 2002, Farley et al. 2014, 2015]

Species	Longevity / Maximum Size	Maturity (50 per cent)
Southern Bluefin Tuna	40+ years; ~1 900 mm FL	~10–12 years; 1 580–1 630 mm FL

Distribution of reported commercial catch of Southern Bluefin Tuna

	Commonwealth
Commercial
Pole and Line
Trolling
Purse Seine
Longline (Unspecified)

Method	Commonwealth
Commercial
Area restrictions
Catch limits
Individual transferable quota

	Commonwealth
Commercial	17.10Kt

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. Recreational catches reported here are from surveys.
Commonwealth Recreational and Indigenous Recreational and Indigenous fishing sectors reported here are New South Wales, Queensland, South Australia, Tasmania, Victoria and Western Australia. Measures listed here exist in at least one of these jurisdictions.
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.
Commonwealth – Commercial (catch) Catches reported for the Commission for the Conservation of Southern Bluefin Tuna (CCSBT) are for 2018, the most recent year available.

Commercial catch of Southern Bluefin Tuna - note confidential catch not shown.

1. Commission for the Conservation of Southern Bluefin Tuna 2020, Report of the twenty fifth meeting of the Scientific Committee, online meeting, 7 September 2020
2. Commission for the Conservation of Southern Bluefin Tuna 2021, Report of the twenty sixth meeting of the Scientific Committee, online meeting, 23–31 August 2021.
3. Davis, T, Farley, J and Gunn, J 2001, Size and age at 50% maturity in SBT: an integrated view from published information and new data from the spawning ground, CCSBT-SC/0108/16, Tokyo, Japan, 28–31 August 2001.
4. Evans, K, Patterson, TA, Reid, H and Harley, SJ 2012, Reproductive schedules in southern bluefin tuna: Are current assumptions appropriate? PLoS One, 7(4):e34550.
5. Farley, JH, David, TLO, Bravington, MV, Andamari, R and Davies, CR 2015, Spawning dynamics and size related trends in reproductive parameters of southern bluefin tuna, Thunnus maccoyii, PLoS One 10(5): e0125744.
6. Farley, JH, Eveson, JP, Davis, TLO, Andamari, R, Proctor, CH, Nugraha, B and Davies, CR 2014, Demographic structure, sex ration and growth rates of southern bluefin tuna (Thunnus maccoyii) on the spawning ground, PLoS One 9(5): e96392.
7. Hillary, RM, Preece, AL, Davies CR, Takahashi, N and Itoh, T 2020, The assessment of stock status in 2020, paper CCSBT-ESC/2008/12 (Rev.2) for the twenty fifth meeting of the CCSBT Scientific Committee, 31 August–5 September 2020, online meeting.
8. Laslett, GM, Eveson, JP and Polacheck, T 2002, A flexible maximum likelihood approach for fitting growth curves to tag-recapture data, Canadian Journal of Fisheries and Aquatic Sciences, 59: 976–986.
9. Patterson, H, Williams, A and Mobsby, D 2020, Southern Bluefin Tuna Fishery, in H Patterson, J Larcombe J Woodhams and R Curtotti (eds), Fishery status reports 2020, Australian Bureau of Agricultural and Resource Economics and Sciences, Canberra, xxx-xxx.
10. Patterson, TA, Eveson, JP, Hartog, JR, Evans, K, Cooper, S, Lansdell, M, Hobday, AJ and Davies, CJ 2018, Migration dynamics of juvenile southern bluefin tuna, Scientific Reports, 8: 14553.
11. Proctor, CH, Thresher, RE, Gunn, JS, Mills, DJ, Harrowfield, IR and Sie, SH 1995, Stock structure of the Southern Bluefin Tuna, Thunnus maccoyii: an investigation based on probe micro analysis of otolith composition, Marine Biology, 122(4): 511–526.
12. Tracey, SR, Lyle, JM, Stark, K, Gray, S, Moore, A, Twiname, S & Wotherspoon, S 2020, National survey of recreational fishing for southern bluefin tuna in Australia 2018–19, University of Tasmania, Hobart.