International Tuna Day is celebrated every year on 2 May. It celebrates the different species and raises awareness of their conservation and consumption through sustainable fishing and stock management.
Following the alarming figures revealing the rate of overfishing of various tuna species, the United Nations General Assembly declared 2 May the official date of World Tuna Day on 7 December 2016. The aim is to combat not only the depletion of stocks and the decline of species around the world, but also tuna fishing practices that destroy marine biodiversity and violate human rights.
This day is a reminder of the crucial importance of preserving the different species of tuna, ensuring compliance with the laws of the sea (in particular the United Nations Convention on the Law of the Sea and the United Nations Fish Stocks Agreement), ensuring sustainable fishing that respects ecosystems and putting an end to overfishing.
The latter is one of the United Nations Sustainable Development Goals (SDGs) for 2030. 2 May is an opportunity to raise awareness around the world of the essential role this fish plays for the environment, the world’s oceans and the countries where tuna fishing has an impact on their economic development and food security.
Everyone can take part in World Tuna Day by raising awareness, learning about fishing methods and buying certified sustainable products. Every year, the Marine Stewardship Council reminds us of the need to take action to protect this fish. One of the causes of overfishing is increasing international demand.
What are the characteristics of tuna?
Tuna is a very fast animal and can only be caught in the wild. They are carnivorous and feed mainly on crustaceans, squid and other fish such as mackerel. There are several species of tuna, divided into sub-categories or populations. For example, there are three species of bluefin tuna: Atlantic bluefin, Pacific bluefin and southern bluefin. The sub-categories include western Atlantic bluefin tuna, southern Pacific bluefin tuna and central western Pacific bluefin tuna.
Bluefin tuna are at the top of the food chain. Its main predators are sharks, certain whale species and marlin. It accounts for more than 8% of global trade in marine products and 20% of the market value of all marine capture fisheries, according to the United Nations. By 2027, sales of canned tuna could be worth an estimated US$11.89 billion. The different species consumed include albacore, skipjack, bigeye, bluefin and yellowfin tuna. Certain populations of the latter three species are among the most vulnerable to overfishing. In 2011, the MSC reported that Atlantic bluefin tuna had lost up to 50% of its population in a decade.
Tuna and related species are rich in nutrients, protein, vitamin B12 and omega-3, and low in fat and calories. However, they may contain traces of mercury as a result of their diet.
Why is tuna threatened by overfishing?
There is an ever-increasing global demand for tuna. It is a highly valued fish. Recent estimates suggest that around 22% of tuna stocks are at risk of overfishing and 13% are overexploited. In 2017, almost a third of stocks of the most common species were fished unsustainably. A stock is an area where the population of a species is exploited, where the number of fish and the reproduction and mortality rates are monitored and evaluated according to the principle of fisheries management in order to avoid overfishing and poor reproductive conditions. Eggs, larvae and juveniles are not affected. According to the T-Regional Fisheries Management Organisations (T-RFMOs), there are 23 stocks in the world: 4 stocks of patudo (bigeye tuna), 4 of bluefin tuna, 4 of yellowfin tuna, 6 of albacore tuna and 5 of skipjack tuna.
In 2025, according to the ISSF (International Seafood Sustainability Foundation) report, 65% of tuna stocks will be in a healthy state, 9% will still be overexploited and 26% will be somewhere in between. In terms of fishing effort, 91% of stocks are not overexploited, but there are still critical situations. Some populations of bluefin tuna and bigeye tuna are particularly vulnerable. This report, entitled “The state of world tuna fisheries in March 2025”, has been scientifically verified to ensure its unquestionable reliability. More than 7 million tonnes of tuna are caught each year. (5.2 million in 2023 according to the ISSF). One of the destructive consequences of fishing and overfishing is bycatch, the accidental capture of other animals such as dolphins, sharks, birds, turtles and endangered species. Overfishing has a dangerous impact on the food security and economic development of countries whose tuna resources are crucial.
The different fishing methods
Tuna is a fast moving fish. The different species of tuna and tuna-like fish can be caught in almost all oceans and seas. More than half of the world’s tuna is caught in the Central West Pacific. Tuna is caught using a variety of methods: purse seine, pelagic longline, pole and line. The latter two are used to catch fish one at a time. Pole-and-line fishing is characterised by the use of water and small baits to attract tuna. In purse seine fishing, a large net attached to a boat is dragged across the water, closing like a purse to catch as many fish as possible. This net can be up to 2,000 metres long and 200 metres deep. Pelagic longlines are a system of lines with baited hooks at depths of between 50 and 300 metres. The lines can be up to 100 kilometres long. They are set for several hours before being removed. It is a traditional fishing technique.
Driftnet fishing is banned in the European Union and several other countries around the world. This fishing technique has caught animals other than the target species, such as dolphins, sharks, seabirds and sea turtles. This is known as ‘bycatch’. The system of Fish Aggregating Devices (FADs) is highly controversial for the same reasons. By-catch endangers other species and weakens tuna stocks by accidentally catching juvenile fish. FADs are artificial wooden structures that float on the surface and to which nets are attached, like a kind of raft. Longlines and purse seines are also subject to by-catch. They must therefore be managed sustainably to avoid endangering potentially vulnerable species.
Which tuna species are most vulnerable to overfishing?
The species most at risk are yellowfin tuna, found in the Indian Ocean, bigeye tuna and several populations of Pacific bluefin tuna (there are three species of bluefin tuna: Atlantic bluefin tuna, Pacific bluefin tuna and southern bluefin tuna. Pacific bluefin tuna can travel more than 8,000 km to feed). The Atlantic bluefin population declined drastically in the 1990s before gradually improving. Of the 4 bluefin tuna stocks, MSC data shows that by 2021, the species will move from ‘vulnerable’ to ‘least concern’ in the IUCN classification. Southern bluefin tuna is still threatened, although it is no longer critically endangered. However, tuna are facing climate change. Warmer waters are forcing fish to move to colder waters, especially to spawn. The heat affects their metabolism.
Pacific bluefin tuna is highly sought after for sushi and sashimi. Rising global demand for sushi is one of the reasons why the species was on the brink of extinction around 2010. Thanks to the introduction of fishing quotas in various countries, increased surveillance of illegal fishing and stricter regulations, Pacific bluefin tuna populations have returned to less alarming levels. However, several stocks are still at low levels. According to the IUCN, “the species remains severely depleted, with less than 5% of its original biomass remaining”.
The eastern population of Atlantic bluefin tuna has increased by 22% over the last 40 years, but the indigenous population in the western Atlantic has declined by more than half over the same period.
Bigeye tuna is overfished and subject to illegal, unregulated and unreported (IUU) fishing. The IUCN will update the Red List in 2021. The introduction of quotas and the fight against illegal fishing and for sustainable fishing are helping to increase the number of stocks. Bigeye tuna is listed as vulnerable.
Yellowfin tuna is overfished in the Indian Ocean. According to Planet Tracker, yellowfin tuna stocks could ‘collapse’ by 2026 unless action is taken quickly to reduce overfishing.
Which countries are overfishing tuna?
The critical situation of bluefin tuna in the Pacific has forced Japan to set very strict fishing quotas. These quotas have recently been increased.
Yellowfin tuna off the coast of Somalia face the destructive methods of many Chinese boats. Illegal fishing has reached alarming proportions. The consequences are disastrous, both for the marine environment and for the local population, for whom tuna is a major source of food. This fish is also in demand in other parts of the world and represents a significant economic value. Its endangerment affects not only the countries of the Horn of Africa, but the whole world.
In addition to the food situation, the overfishing of yellowfin tuna by Chinese vessels is having an alarming economic impact. Illegal, unreported and unregulated (IUU) fishing costs Somalia around $300 million a year. Overfishing is often carried out by organised criminal groups, making it difficult to combat this scourge. The Somali Ministry of Fisheries and Blue Economy and the UNODC (United Nations Office on Drugs and Crime) Global Programme to Combat Crime met in 2023 to take decisions on improving fishing methods and law enforcement. A partnership with Turkey is also being strengthened to improve maritime safety. The Somali government is taking many measures to combat illegal fishing. Unfortunately, there are still problems with corruption and a lack of transparency in fishing agreements.
The fishing methods used by Chinese vessels are devastating to the Somali seabed and fish stocks. They use purse seines, longlines, bottom trawling, which destroys the ecosystem, and dynamite fishing.
Indonesia has several species of tuna: yellowfin, skipjack and bigeye. The country is faced with IUU fishing and its economic consequences. Tuna stocks are threatened by overfishing. But this illegal practice also leads to criminal activities such as slavery, human trafficking, drug trafficking and forced labour. International cooperation must be strengthened to put an end to these activities. A Greenpeace Southeast Asia report entitled « Netting Profits, Risking Lives: The Unresolved Human and Environmental Exploitation at Sea », reveals that between 2019 and 2024, vessels flying the Taiwanese flag were involved in forced labour and “withholding identity documents”. The report is based on complaints made by around ten Indonesian fishermen to the Indonesian Migrant Workers’ Union (SMBI). It also reveals cases of shark finning. Four of these vessels sold their goods to the American canned tuna brand Bumble Bee.
What is being done to tackle overfishing?
Over the years, the imposition of fishing quotas, global monitoring of stocks and cooperation between countries and international NGOs have helped to combat overfishing, with encouraging results. Monitoring fishing methods to minimise the catch of threatened or unwanted species or bycatch also helps to move towards sustainable fishing. By-catch can be minimised by using purse seines or longlines. Tuna caught responsibly using these methods is certified by the MSC, the seal of sustainable fishing.
By 2023, New Caledonia will be using longliners ‘certified as responsible fisheries‘. It is considered ‘an example of sustainable fishing in its maritime zone’.
With regard to purse seine fishing, the use of nets with different structures could prevent the capture of dolphins and other animals by allowing them to escape.
Fish aggregating devices (FADs), which are highly controversial, are also being considered. However, it is possible to manage them in a way that is considered sustainable.
Some countries, such as Madagascar, are introducing taxes. By 2022, Madagascar had become the second country with the highest access fee for tuna fishing in the Indian Ocean. The first was Mauritius. European trawlers will have to pay Madagascar 220 euros per tonne in 2022, up from 142 euros.
Umar Papalia, an Indonesian fisherman who has witnessed the decline of yellowfin tuna, stresses the importance of sustainable aquaculture in conserving the fish. Today, more than 96 nations are committed to the conservation of various tuna species.
What organisations fight overfishing?
Several NGOs and jurisdictions are fighting overfishing and enforcing the law of the sea. The 1982 United Nations Convention on the Law of the Sea (UNCLOS) established the United Nations Fish Stocks Agreement, which came into force in 2001. It ensures the conservation and sustainable management of fish stocks.
The Food and Agriculture Organization of the United Nations (FAO) is involved in many projects and programmes. One of these is the FAO Common Oceans Tuna, which aims to achieve sustainable tuna fishing for all stocks by 2027. Some of the results have been positive, notably the proven reduction of overfishing. The Joint Oceans Programme aims to ensure the sustainable management and exploitation of stocks and the conservation of biodiversity by reducing the negative impact of tuna fishing on the marine ecosystem. The 1995 FAO Code of Conduct for Responsible Fisheries, or 1995 FAO Code, is considered a reliable reference and is widely used around the world.
In 2020, a UN report shows that the number of overfished tuna stocks fell from 13 to 5 between 2014 and 2019. This reduction was made possible by five tuna RFMOs (Regional Fisheries Management Organisations) around the world, as well as a number of intergovernmental organisations, civil societies and private companies.
The MSC, a seal of approval for sustainable fishing
The Marine Stewardship Council (MSC) is an international non-governmental organisation working to combat overfishing and conserve the world’s marine resources. It has set up a programme to certify sustainably caught seafood. The MSC defines three different criteria for certified sustainable products: the state of the stock, its environment and the fishing management methods. The MSC ‘Blue Fish’ label therefore certifies tuna that has been caught in a sustainable manner that takes into account and respects its impact on the environment. Consuming MSC-labelled tuna contributes to the conservation of tuna species.
According to the MSC’s Sustainable Tuna 2024 report, sales of MSC-certified tuna will increase by 10% between 2022-2023 and 2023-2024. Sales will increase from 196,363 tonnes to 217,300 tonnes. Based on reliable and verified analysis, the report highlights the growth in sustainable tuna consumption around the world and the widespread awareness of the need to conserve the species.
About the International Seafood Sustainability Foundation
The ISSF was founded in 2009 by an international alliance of leading scientists, environmentalists and seafood industry leaders. It was born out of a shared concern for fisheries and their future, and a desire to take action. They conduct research, advocate for sustainable fishing and ecosystem conservation, and propose responsible practices to a range of stakeholders in the marine environment: boat owners, fishermen, companies, organisations and associations. The ISSF regularly publishes reports on the state of fish stocks, based on the latest scientific data.
International Commission for the Conservation of Atlantic Tunas (ICCAT)
ICCAT is a regional fisheries management organisation. It is responsible for the conservation of tuna and other fish in the Atlantic Ocean and adjacent seas (including the Mediterranean). It assesses the state of tuna populations on the basis of scientific data and leads discussions with member countries to set fishing quotas (or TACs, Total Allowable Catches) and methods to minimise by-catches.
What are the areas for improvement?
In March 2025, the ISSF published a report on the state of fish stocks. It stated that 87% of the world’s tuna catches came from stocks considered to be at healthy levels. The November 2024 report presented similar data. Overexploited stocks account for 2% of global catches, a drop of 8 percentage points since the last report. The percentage of “intermediate” catches has increased to 10%. All these changes concern yellowfin tuna in the Indian Ocean.
The regulation of fishing and exploitation has had a major impact on the recovery of tuna species. Recent data from the IUCN Red List of Threatened Species show an improvement in the situation of tuna, mainly due to the introduction of fishing quotas. However, 28% of the species studied by the IUCN are still threatened. According to Dr Bruce B. Collette, Chair of the IUCN SSC Tuna and Roosterfish Specialist Group, ‘tuna species migrate across thousands of kilometres, so coordinating their management globally is also key’.
