When they are about 40 to 50 cm long and weigh about 3 kg, they move either east through the Great Australian Bight towards New Zealand or west through the Indian Ocean towards South Africa. The SBT commercial fishery Commercial fishing for SBT in Australian waters began on a large scale in the 1950s. Since then, SBT have been fished by Australian and Japanese boats. The Japanese boats that fish in Australian waters are strictly controlled by management arrangements administered by the Australian Fisheries Management Authority. Today, SBT are caught in the AFZ off South Australia, Tasmania, southern Western Australia and New South Wales.
Japanese boats use longlines only.
The catch of SBT around the world reached about 80,000 tonnes in the early 1960s. After this time catches declined, which reflected declining stock condition and the application of quota limits by Japan, Australia and New Zealand, whose current catch is about 11,750 tonnes per year. Recently, SBT have been farmed. This involves catching the fish and putting them in floating cages anchored to the ocean floor. The tuna are then fattened for several months and when market prices are good, they are sold.