Photo: Dennis C.J. / Research Matters
Doesn’t observing ‘World Tuna Day’ sound bizarre? Wondering if we would end up with ‘World Sardine Day’ and ‘World Mackerel Day’ next? If we don’t stop our reckless fishing ways, we might soon have them too!
The United Nations decided on December 8, 2016, to establish and observe the first ‘World Tuna Day’ on May 2, 2017. But why specifically tuna?
Tuna are among the world’s most popular, and hence commercially valuable fishes. They are big, salt-water fish found in all of our oceans and seas. People buy tuna in its fresh, frozen and canned form. They are eaten in salads, sandwiches, burgers, sushi and even in grandma’s age-old curries.
According to the Food and Agricultural Organisation (FAO), in the year 2009, the annual global catch of tuna and tuna-like species reached nearly 7 million tonnes. In 2012, the annual global sales value of tuna was estimated to be US$ 33.36 billion. These astronomically high numbers are a result of overfishing – where fish stocks are reduced to below acceptable levels. For instance, the population of the Pacific Bluefin tuna in particular, which has been overfished for the last 70 years, has dropped by a shocking 97% as of 2016.
Tuna and its taste
So why do people love tuna - a fish that was once used in cat food? According to Andrew F. Smith who teaches Food Studies at the New School University in New York and author of the book ‘American Tuna: The Rise and Fall of an Improbable Food’, tuna became popular because it was cheap, yet tasted like chicken – hence called ‘chicken of the sea’. But that only applies for processed tuna.
During World War I, European countries and the US government decided to buy canned tuna as a cheap protein substitute to feed their troops. When soldiers returned from war, they continued to eat tuna. In America, this slowly resulted in the displacement of salmon as the most preferred fish.
Today, there are fifteen species of tuna across five genera. The Albacore tuna, Southern Bluefin tuna, Bigeye tuna, Pacific Bluefin tuna, Atlantic Bluefin tuna, Blackfin tuna, Longtail tuna and the Yellowfin tuna constitute 'true tunas', while the Slender tuna, Bullet tuna, Frigate tuna, Mackerel tuna, Little tunny, Black Skipjack tuna and Skipjack are the ‘other tunas’. Of these, the smallest is the Bullet tuna which grows to a maximum of 1.6 feet and the largest is the Atlantic Bluefin tuna, which can grow up to 15 feet and weigh around 600 kg. The true tunas are more specialised than the other tunas in having more pectoral fin rays (30-36 or 23-27) and the first vertebrae completely sutured to the skull.
One of the most peculiar characteristics of tuna is their ability to maintain a higher temperature of certain parts of their body, than the surrounding seawater. However, they are unable to maintain this temperature in a narrow range, which is the typical characteristic of true endotherms like birds and mammals. Tuna are hence, ‘partial endotherms’.
Living in the shadow of extinction
Unfortunately, the more glaring characteristic of tuna is that today, many of its species are under the risk of extinction.
The IUCN (International Union for Conservation of Nature) Red List, the world’s most comprehensive inventory of the conservation status of biological species, classifies the Southern Bluefin tuna as ‘critically endangered’, while the Atlantic Bluefin tuna is listed an ‘endangered’. The Bigeye tuna and the Pacific Bluefin tuna have both been placed in the ‘vulnerable’ category and Albacore and Yellowfin tuna are close to being ‘under threat’. The reason for the threat of extinction for one of the most commercially important fishes in the world is obvious -- rampant overfishing.
Dr. Kent Carpenter, Manager of IUCN’s marine biodiversity unit and author of a study on the status of tuna stock published in the journal ‘Science’ had once said in an interview - “All three Bluefin species are susceptible to collapse under continued fishing pressure. The Southern Bluefin has already crashed, with little hope of recovery”.
According to the FAO, most tuna stocks have been exploited to the extent that further expansion in their fishing is impossible and some species, like the Bluefins are over-exploited.
A common method used to catch Bluefins is ‘purse seine fishing’, where a large wall of netting, called a seine, is deployed from a fishing vessel around a school of fish. Along the bottom end of the seine are a series of rings, through which runs a lead line. This line is pulled, closing the seine at the bottom, thus preventing the fish from escaping. The catch is then harvested by hauling the seine in. In cases where some fish species school with others, this method ends up catching them too. Hence, when purse seine fishing is used to catch tuna, others like rays, sharks, turtles and young tuna are also caught.
But it’s difficult to make countries drop trade in the threatened tuna altogether due to their high value. The Bluefin tuna in particular, is so prized among the Japanese that the first Bluefin of the year 2013 was auctioned off for a whopping $1.76 million.
Saving tuna - a race against time
It’s in this scenario that the United Nations voted to declare May 2nd of every year as ‘World Tuna Day’. This move by the UN affirms the value of tuna in food security and in maintaining the livelihoods of many people across the world, while also recognising the need to conserve the species. It was the PNA (Parties to the Nauru Agreement), a group of nations in Oceania that have an agreement for cooperation in the management of their fisheries, that had been pushing the UN to declare it as an internationally recognised event for the past five years.
Today PNA controls the world’s largest ‘sustainable’ tuna purse seine industry, with active involvement in conserving tuna, while acknowledging that it is a vital food resource. The parties have placed closures on high seas fishing, controls on FADs (Fish Aggregating Devices) that increase the catch and have also agreed on a limited number of days in a year for fishing, based on scientific data regarding tuna stocks.
The declaration of World Tuna Day is a welcome effort that will bring more attention to conservation measures that are taking place for tuna and which will shed some light on the seriousness of the issue to the general public. As for how ordinary citizens like us can help save tuna, just eat less tuna -- especially the ones whose populations are or are soon becoming unstable. When the buying stops, the selling will too!