Port Lincoln southern bluefin tuna fishing seriously cut back by catch quotas in 1980s to save the species

The rapid decline in the overall southern bluefin tuna catch since South Australia joined the industry from Port Lincoln in the 1950s. Japan was the dominant in the overexploitation of the species.
Inset image of Port Lincoln fishing vessels by Bruce Elder of Aussie Towns

The drastic effect the fishing industry, heavily based in South Australia at Port Lincoln, was having on the biomass of southern bluefin tuna (Thunnus maccoyii) forced national and international quotas on catches in the 1980s.

In 1984, individual transferable quotas were allocated by the Australian government to fishermen to prevent further exploitation and allow the species to recover. These initial quotes were later further reduced. Between 1983 and 1988, fishermen were unable to catch even the lower quotas, showing how much the fishery had been overexploited.

In 1989, a conference between the three southern bluefin tuna fishing main nations – Japan, Australia and New Zealand – agreed that the total combined yearly quota for all three would be limited to 11,750 tonnes. This was 8,000 tonnes below the peak of Australia’s southern bluefin tuna catch and 30,000 tonnes less than Japan’s peak catch.

In 1994, the informal management of the fishery between the three countries was formalised with the convention for the conservation of southern bluefin tuna. Since then, the convention has managed the fish stock internationally. It grew to seven members: Australia, Japan, New Zealand, South Korea, Indonesia, Taiwan and the European Union, with Philippines and South Africa as cooperating nonmembers. The total 2016-17 allocation proposed for these nine entities combined was 14,627 tonnes.

An Australian government harvest strategy in 2011 involved collecting data to help assessment of the southern bluefin tuna by an international scientific committee. The individual bluefin tuna proved very effective in recovering the species biomass. In 2014, the international convention’s scientific committee confirmed a strong recovery.

Also in 2011, the convention adopted a management procedure setting the quota based on the key data trends. Since then, the international quota increased by 55% and the Australian quota by 41%, based on improved stock numbers. The 2014 stock assessment suggested the spawning biomass was at nine per cent of its original biomass, and below the interim target of 20% of original biomass target for a sustainable yield.

But there was improvement from the 2011 stock assessment in 2014 and the catch quotas provided a 70% probability of rebuilding to the 20% target by 2035.