World Tuna is celebrated on 2 May every year, and this year we are have valuable insight from WWF’s Global Tuna Leader, Marcel Kroese. Marcel is stationed with the Marine Programme at WWF-SA so we are lucky to have him in our midst!
You may or may not know that there are many different species of tuna that are consumed in South Africa. Five species are listed on the WWF-SASSI app and website, each having different sustainability statuses. Some species even appear on more than one colour list depending how they are caught and where they are from.
Although the end value of canned tuna accounts for billions of dollars, we will be the first to highlight that tuna fisheries are not just important economically and for food security but such marine megafauna (large-bodied organisms that weigh or exceed 45kg) in the ocean ecosystem are critical. Scientists reveal that megafauna affect ocean ecosystems by consuming large amounts of biomass; transporting nutrients within and between habitats via excretion; connecting ocean ecosystems via long-distance migration; and physically modifying habitats by way of their feeding, locomotion, and mortality.
Before we get into the situation of our tuna in South Africa it is important to know what we refer to by ‘stock’. Fish stocks are subpopulations of a particular species of fish, for which certain parameters (growth, recruitment, mortality and fishing mortality) are regarded as factors determining its dynamics. We can talk about a stock being healthy, and on the other hand some stocks that are not doing too well. Globally, 65% of the tuna stocks are at a healthy level of abundance, 17.5% are overfished and 17.5% are at an intermediate level, where the stock’s status is not apparent. In 2018 the global catch of major commercial tunas was 5.1 million tons, composed of 58% skipjack tuna, followed by yellowfin (29%), bigeye (8%) and albacore (4%). Bluefin tunas accounted for 1% of the global catch. Catches of tuna have almost doubled since the 1980’s, with the biggest increase in skipjack tuna catches. Most skipjack tuna are canned. Skipjack stocks contribute more than one half of the global catch of tunas and the most often overfished stocks are Bluefin, yellowfin and bigeye which results in 15% of the total tuna catch.
One of our favourite fish, the yellowfin tuna are caught and originate from the Indian Ocean, even when it is caught in Hout Bay! This is due to the feeding pattern of Yellowfin, which travel down the warm Agulhas current to the Atlantic Ocean. Unfortunately a red flag has been raised for this species in the Indian Ocean as stocks are predicted to decrease significantly. The impact of these catches are exacerbated by the use of Fish Aggregation Devices (FADs) in the purse seine fisheries and scientists estimate that this could cause yellowfin stocks to crash as soon as 2027. This paints a bleak picture for yellowfin tuna with its high catches, in addition to the stock already being under considerable pressure.What’s worse is that juvenile yellowfin tuna often school together with the same size, but mature skipjack tuna, and both species are caught together. Skipjack tuna is currently facing a voluntary catch limit which is 30% higher than acceptable catch limits. This was noted in 2018 when the Indian Ocean Tuna Commission (IOTC) set the limit for the 2018 – 2020 management period.
In 2019, WWF and other conservation NGOs called for a firm yellowfin tuna rebuilding plan at the IOTC meeting in India. No heed was given to this request, despite retailers increasingly abandoning Indian Ocean yellowfin from their sourcing practices. The fishery responsible for much of the juvenile mortality – the skipjack FAD fishery, continues unabated. In 2020 WWF will call for even stronger measures to protect the vital megafauna tuna stocks, that make such a valuable contribution to ocean health and mitigating climate change in the Indian ocean.
This will ensure that this loved species canned, seared or in sushi will continue to remain in our seas and on our plates