SANBI IDentifyIt - Species Southern Bluefin Tuna - Thunnus maccoyii Geographic location / distribution Habitat: Found throughout the southern ocean, in the Pacific, Indian and Atlantic Oceans, southern bluefin tuna are confined to temperatures of 5-20 C. The only known breeding area is in the Indian Ocean, south-east of Indonesia. Near Southern Africa, SBT is mainly found south of South Africa's EEZ, in cool temperate waters, and is therefore seldom caught by South African longliners. Catches of this species peak between July and August when southern bluefin migrate through South Africa's EEZ. Fishery Southern Bluefin Tuna is caught by the tuna/swordfish longline fishery in South Africa, and are very rarely caught in the Tuna Pole fishery. The target market is the Japanese sashimi market. The tuna pole fishery is a small fishery which lands albacore and yellowfin fresh for the export market, and has a fishing season from October - March each year. Pole boats fish for up to 5-10 days at a time and will not venture as far offshore as longliners. They are less likely to catch bluefin than longliners. Using a pole and line is a selective form of fishing and not much bycatch is caught. However, seabirds and sharks do occasionally get caught on the line and should be released alive. Other fish species are caught and are managed by catch limits: Daily bag limit of 10 yellowtail per crew member Species not allowed to be caught: Chokka and Mackerel spp. Domestic and joint venture vessels as well as foreign vessels may land SBT at our port along with the targeted catch of Yellowfin, Bigeye and Albacore Tuna, mostly aimed for the export market. Longlining is not a very selective form of fishing and many species are caught accidentally on the hooks. Bycatch species in this fishery include: billfishes (swordfish, marlins etc), seabirds, turtles and sharks. Bycatch restrictions therefore exist to protect vulnerable species: The bycatch of billfish cannot exceed 10% of the total tuna catch A precautionary catch limit of 25 seabirds has been set for tuna longline vessels, after which further management restrictions are enforced Shark fins need to be landed with their trunks, with the fins not exceeding 5% of the weight of the trunk Any Bigeye, Swordfish or Southern Bluefin tuna landed must be accompanies by the relevant RFMO (ICCAT, IOTC or CCSBT) catch statistical document. Size limits Southern bluefin tuna >6.4kg Bigeye tuna >3.2kg Yellowfin tuna >3.2kg Swordfish >119cm LJFL / >18kg dressed Marlins >210cm LJFL Stock status Critical The status of the southern bluefin tuna (SBT) stock is at a critical stage resulting in a reduction in the global SBT catch in 2010/2011. Fisheries management Southern Bluefin falls within the management of the large pelagic fishery, and due to its widespread and migratory habits in the entire southern ocean, it is managed by Regional Fisheries Management Organisations, one of which is dedicated entirely to the southern bluefin (the CCSBT - Committee for the Conservation of Southern Bluefin Tuna). South Africa is a member of ICCAT and a co-operating non-member of IOTC and CCSBT. Although RFMO's manage high
seas fisheries, management recommendations and resolutions are implemented by South Africa through national legislation and permit conditions. The Tuna fishery is managed by a Total Allowable Effort (TAE), meaning that instead of setting a limit on the catch, a limit is set on the number of rights holders allowed to catch tuna. Currently there is a limit of 200 rights holders in SA (including pole and longline). However, Bluefin is further managed within this effort limitation by a TAC, set by the RFMO's at a precautionary total catch of 40 tons for the SA fleet. Any bluefin landed must be tagged with a unique code and the CCSBT catch documentation must be completed and submitted to DAFF. Maturity and Sizes Southern Bluefin reach maturity after 11 years (believed to be around 130cm, at 40kg). Maximum fork length is 225 cm. Other similar species Thunnus alalunga - Albacore/Longfin Tuna Thunnus albacares - Yellowfin Tuna Thunnus obesus - Big-Eye Tuna Katsuwonus pelamis - Skipjack Tuna Could be confused with It is impossible to tell the difference between Bigeye and Bluefin without a DNA sample. References SASSI status http://www.wwfsassi.co.za/?m=5&s=5&idkey=1118 FAO fact sheets http://www.fao.org/fishery/species/2498/en Fishery Resource Monitoring System Fact Sheets: http://firms.fao.org/firms/resource/9/en ICCAT Tuna fact sheets. ICAT Manual. January 2010. FAO. 2006-2010. Fisheries and Aquaculture Department. Biological characteristics of tuna/individual species sheets. FI Institutional Websites. Text by Michel Goujon and Jacek Majkowski. In: FAO Fisheries and Aquaculture Department[online]. Rome. Updated 24 February 2010. [Cited 30 November 2010]. Website: http://www.fao.org/fishery/topic/16082/en Southern Bluefin Tuna Photo: Peter C. Young
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