Southern Bluefin Tuna (SBT), Thunnus maccoyii, is a migratory and valuable pelagic fish. SBT ranges widely across the high seas regions of the southern hemisphere including territorial seas of countries such as Australia, New Zealand and South Africa.
SBT has a single spawning ground in the waters south of Indonesia (refer below) between approximately 7 degrees and 20 degrees south. Adult SBT migrate from southern feeding areas to the spawning ground between September and April.
The larvae and juvenile fish are swept south by the Leeuwin current along the Western Australian coastline, and reach the Great Australian Bight as 1 to 2 year olds. At this point, depending on a range of factors SBT either push west into the Indian Ocean or east into the Great Australian Bight.
SBT is a long-lived species, living up to 40 years. They have a lengthy pre-maturity period and mature at lengths of about 120-130cm and 7-8 years of age.