Tuna

There are five commercially fished tuna species: Atlantic bluefin tuna, Skipjack tuna, Yellowfin tuna, bigeye tuna and Albacore tuna. The bluefin and bigeye are the biggest tuna species, most exclusive and high valued and thus also most overfished and vulnerable to IUU fishing. We don’t recommend eating these species.

The tuna species most found in cans is the smaller Skipjack or Albacore tuna. 89% of the skipjack stocks worldwide are in healthy condition and 11% in intermediate condition. Of the Albacore stocks there 5 out of 6 healthy. The Albacore stock in the Mediterranean is not doing well. However, the fishing techniques used to catch these tuna are not all good. 80% of the skipjack is caught by purse seines and 65% of Albacore with longlines. Both techniques have bycatch of undersized tuna or vulnerable shark species. The most sustainable type of fishing for tuna is the pole and line method which is used for 8% (skipjack) and 15% (albacore) of the catches. There is little bycatch in this fishery where the fish are taken one by one.

Tuna steaks found at your fishmonger or restaurant, are almost always Yellowfin Tuna. Of the worldwide catches of yellowfin tuna, 70% comes from healthy stocks. Unfortunately, the other 30% comes from stocks that are severely overfished.

If you want to continue eating tuna, we recommend choosing MSC certified steaks or cans to ensure the tuna comes from a healthy stock.

In tuna fisheries there are 3 main techniques used, purse seining with or without fish aggregating devices, longlines and pole and line. Because of the high value of bluefin tuna, in the Mediterranean even small plans are used for aerial spotting of tuna to point the fishing vessels to the right location.

Purse seines

Purse seines are the main fishing techniques used to harvest tuna. For all tuna species the catches are done for more than half (50-80%) with purse seines. Many purse seine fisheries use Fish Aggregating Devices. These are floating objects that attract sealife. Tuna gather under these FADs, which makes it easier to find and catch them. FADs are usually equipped with satellites to provide fishers with geo-location information and estimates of resulting biomass underneath. The FADs make purse seining much more effective but causes high levels of bycatch including Endangered, Threatened and Protected species such as whitehead and hammerhead sharks. Purse seining can also be done with free swimming schools, this is seen as a more sustainable type of fishing because bycatch rates are much lower.

Longlines

After purse seining, the longline is the second most used fishing technique for tuna fisheries. 65% of all Albacore tuna is caught by longlines and for bigeye and bluefin tuna this is 30%. Longlining is not used in the skipjack fisheries and for yellowfin it represents less than 10% of the catch.

Longlining consist of a main line with branchlines attached. The branchline is made up of a shorter line, leader and a hook. The line is kept near or below the surface with floating buoys. Depending on the depths the gear is deployed, there are different target species. In the upper part yellowfin tuna is caught, while the line needs to be lowered to target bluefin.

Bycatch of endangered and protected animals such as sharks, seabirds, sea turtles and marine mammals is seen as the most urgent issue with longlining.

Pole & lines

Pole and lines are mostly used to catch albacore (15% of total catches) and skipjack tuna (8% of total catches). Living bait is bought from local fisherman to attract tuna to the boat. When the bait is thrown in the water and the tuna are predating, they are captured by the hand operated lines. The fishery has very little bycatch of ETP species and this can be released alive. Although the environmental impact of this fishing type is low, it can still be used to fish on an overfished stock. Also, there are concerns about the sustainability of the bait stocks that are being used.

There is an enormous amount of scientific data that shows the high levels of bycatch of endangered, threatened and protected species that are caught in tuna purse seining. One of the main places this is seen is through the use of FADs which is most commonly associated with purse seine fishing. The use of FADs has caused a significant increase in catches of the three main target tuna species in the Pacific Ocean (Skipjack, Yellowfin and Bigeye tuna). In the Western Pacific Ocean, FADs are associated with non-target ETP species catches. This included marine mammals, sea turtles, and whale sharks. Species at particular risk are marine turtles. They have bycatch rates associated with FADs that are an order of magnitude higher than other megafauna species. Marine mammal bycatch in purse seines is reportedly low. However, there is little monitoring or accurate reporting, and mitigations measures are not in place.

The level of bycatch of ETP (endangered, threatened and protected) species in longline fisheries is regarded are extremely high. Similar to the purse seine, the species that are most at risk in longlining are elasmobranchs species such as sharks and rays. Unfortunately bycatch of endangered elasmobranchs remains largely unregulated. In some areas no national or bilateral harvest limits have been imposed. This means elasmobranchs in these areas have a much heightened risk of extinction.

Marine mammals are not reported in longline data. This is likely to be due to the lack of observer data and will increase once observations increase. Marine turtles face the risk of being bycatch when they swallow baited hooks of longlines. Drowning also occurs when turtles are entangled in the main float lines. Mortality rates in the longline fisheries are lowest in deeper set lines of around 200-300m depth. These deeper sets however are used to target bigeye tuna and not necessarily skipjack or yellowfin.

In the pole & line fishery there is almost no bycatch of ETP species and non-targeted species can be released alive.

There are a plethora or illegal activities associated with tuna fishing. Human rights abuses are abundant in Tuna fisheries. The country most implicated is Taiwan where forced labour is commonplace and is containing with little to no effective policies. Illegal, unreported and unregulated (IUU) fishing has been well known to occur in tuna fisheries. This is most commonly associated with Bluefin tuna in the Mediterranean Sea, however, as it is the most expensive and prized tuna product for sushi. The extreme prices drive the IUU fishing trade. However, for skipjack and yellowfin tuna, there is less information on IUU fishing partly due to the stocks being in less crisis than Bluefin tuna and therefore have higher legal quotas.

Social issues concerning illegal tuna fishing activity are abundant and are described below.

Some tuna fisheries have been associated with human rights abuses as they are based on the high seas where law enforcement is difficult or absent. Forced labour is the biggest concern for workers in tuna fisheries. International migrants who are forced to work in tuna fisheries are isolated by language as well as physically at sea. A lack of proper grievance mechanisms and communication methods means that migrant workers are more susceptible to abuse.

Taiwan is the second largest longline tuna exporter in the world. They are also the second largest supplier of frozen tuna to Thailand (the largest tuna processors globally). The longline tuna fishing fleets in Taiwan is called the Distant Water Fishing Fleet (DWF). The DWFs has a long history of human rights abuses including beatings and trafficking of Cambodian migrant workers.

As well as forced labour within the fishing of tuna itself, there are numerous nefarious activities within tuna fishing. These include sexual exploitation of children where the beneficiaries partake in tuna fishing. People smuggling and trafficking is also with the remit of organised crime groups such as the Mafia who are using tuna fishing as a cover. Even though these problems are being reported for more than 6 years, policies fail to address them. Supply chains in the US and Europe have been painfully slow in dealing with human rights violations with good practice being the exception. A reason for this is the lack of transparency in the tuna supply chain making effective policies difficult to enable.

Tuna is managed by numerous wide reaching intergovernmental organisations depending on region (see figure 1). Due to the commercial importance of tuna worldwide, there are organisations assigned to dealing with Tuna across the global oceans. The management agencies cover all species of tuna in their designated areas of the coastal oceans and the high seas. In the Indian Ocean, tuna is managed by the Indian Ocean Tuna Commissions (IOTC). The IOTC is made up of members and non-members for the conservation and “appropriate utilisation” of fish stocks. The IOTC is a subsidiary commission of the FAO and compliance with conservation measures is monitored.

In the Atlantic Ocean, tuna is managed by the International Commissions for the Conservations of Atlantic Tuna (ICCAT/CICTA/CICAA). This commission is made up of any government that is a member of the United Nations. The FAO is involved in this commissions in terms of ratification, approval and adherence. The ICCAT has 52 contracting parties made up of American, African and European Nations.

In the Pacific Ocean, the west and central regions are managed by the West and Central Pacific Fisheries Commission (WCPFC). This was born from the Convention for the Conservation and Management of Highly Migratory Fish Stocks in the Western and Central Pacific Ocean (WCPF Convention) in 2004. The WCPFC Convention draws on provisions of the UN Fish Stocks Agreement (UNFSA) as well as characteristics of the western and central pacific region. Members of this commission include Australia, China, Canada, the European Union and the USA.

In eastern pacific, tuna is managed by the Inter American tropical Tuna Commission (IATTC). The members of the IATTC include the European Union, Japan, Canada, USA AND China. There are also cooperating non-members such as Indonesia. As well as tuna, the IATTC has responsibilities to implement the International Dolphin Conservation Programme (IDCP).

The MSC and Dolphin Safe are both internationally recognised certification ecolabels associated with tuna. While the MSC label is a good indication of the overall sustainability of a tuna product, the dolphin safe logo has little sustainability requirements other than that ‘no dolphins’ were captured.

Marine Stewardship Council

The most widely available certification label for tuna is from the Marine Stewardship Council (MSC).  The MSC is a non-profit organisation and is currently the best standard there is for wildcaught fish, although there is critique that the criteria to pass MSC certification should become stricter. For skipjack and yellowfin tuna there are 36 worldwide fisheries that are certified by the MSC as of  June 2022. Most of these fisheries are a combination of both species as they shoal together. However, some of the fisheries are combined with bigeye and albacore tuna, as well as swordfish.

Dolphin Safe/ Dolphin Friendly

The Dolphin Friendly standard has been developed by the American environmental organisation Earth Island Institute (EII). This standard is intended to stop the large amount of dolphin by-catch during fishing for yellowfin tuna in the Pacific Ocean.

This standard requires that fishermen do not use driftnets and ultimately prevent dolphins from being caught. An independent observer must be on board of large fishing boats to assess this.

This quality mark receives a lot of criticism, as companies can say that they are abiding by the rules but there are no independent third-party checks in place. Furthermore, the standard only focuses on the bycatch of dolphins and not on that of other species such as sharks and sea turtles. This means that the certification wrongly suggests that dolphin-friendly tuna is also sustainable tuna. The label is also used for skipjack tuna where dolphin bycatch does not play a role.

The Dolphin Friendly label is not supported by the World Wildlife Fund, Good Fish and Greenpeace. Also some tuna products contain similar ‘dolphin friendly’ labels to bypass the costs for the use of the EII logo, making these labels untrustworthy.

NGOs have raised objections to the certification of several tuna fisheries. In 2017, environmental groups objected to the MSC certification of the tuna fishery in Mexico. This was on the grounds that vessels continue to chase and catch significant numbers of dolphins making it unsustainable.

Furthermore, in 2018, WWF lodged a formal objection to the MSC’s proposed certification of a tuna fishery in the Indian Ocean. The Pesqueras Echebastar skipjack Indian Ocean purse seine fishery was found to be using FADs which the WWF believed should make them ineligible for MSC certification due to the associated bycatch levels. Furthermore, the WWF objection was also based on the overfished status of yellowfin tuna in the Indian Ocean. This is important as it is a bycatch species in the Pesqueras Echebastar skipjack fishery.

In 2020, WWF raised objections to the MSC certification of Atlantic bluefin tuna together with Pew Charitable Trusts. The objections are based on the uncertainty about the recovery of the stock, the failure to include illegal catches in the region and insufficient consideration of by-catches of sharks and other vulnerable marine animals. Despite the objections, the bluefin tuna fishery was certified.

Despite being awarded the MSC label, WWF and Good Fish do not support the certification of Atlantic bluefin tuna.

In global tuna fisheries, fuel accounts for between 30-75% of total annual costs. This amounts to 19 million barrels of fuel and 9 million tonnes of C02 into the atmosphere. Harvesting tuna using purse seines has lower fuel use than longline and pole and line fisheries. In general can be said that frozen tuna has a lower CO2-footprint than canned and fresh products. Purse seining has a significant lower carbon footprint than longlines. In comparison to the production of products such as tofu, fishing for skipjack tuna using purse seine fishing methods has a similar carbon footprint.

About half of the carbon emissions released in the consumption of tuna comes directly from fishing fleets. The rest of the carbon emissions is from electricity, transportation and fuel production.

Bluefin Tuna is farmed in the Mediterranean sea, because of its high value. Currently 0.1% of the wild bluefin catches is used for farming. After catching young bluefin tuna, the fish is placed into nets or cages at sea. The grow-out of bluefin tuna is a highly profitable business. However, this practice puts more pressure on the wild stock and the bluefin tuna needs around 10 till 15 kgs of wild fish to grow 1kg. Other tuna species are not farmed.

Since tuna is such a popular product for Dutch consumers, there are some vegan alternatives on the market. These include products from SeaSoGood’s fish free tuna, Loma’s Tuno and Gourmet Garden’s Vuna. All three products are made from vegetable proteins such as soy, potato and pea. Although these products exist due to a gap in the market and an increasing demand for vegan fish and seafood products, they are not all widely available. It is highly likely that vegan tuna will become more available from numerous brands.

The Japanese cuisine has made eating raw tuna such as sushi and sashimi extremely popular. Raw fish should be very fresh, and fresh yellowfin tuna or bluefin tuna looks soft pink-red or dark red. Tuna meat oxidizes quickly, just like apple. Consumers don’t want that, which is why tuna might be treated with, for example, citric acid to delay browning. When tuna is frozen, the colour changes to gray-brown. Defrosted tuna will then look less fresh.

However, the agents permitted to delay browning can also be used at higher concentrations to mask spoilage. This is dangerous and can result in an allergic reaction to the chemical spoilage process.

How can you test whether tuna has spoilt?

With coloured tuna, it is difficult to determine whether it is still fresh. Unfresh tuna does not smell good, but the additives can sometimes mask that too. When in doubt, put a small piece of raw tuna on your tongue. The chemical process in tainted tuna causes a strong allergic reaction. If it stings, the tuna has gone bad.

It is known that predatory fish such as tuna high in the foodchain store more toxins in their fatty tissues than fish lower in the chain. That is why fish may not be sold in Europe if it contains more mercury, dioxin or antibiotics than the legally established safety levels. The risk of small amounts of dioxins and heavy metals in 1 portion of fatty fish is therefore negligible. The general advice is to eat no more than 4 servings of oily fish per week. For pregnant women, the limit is twice a week and it is also not recommended to eat predatory fish such as tuna and swordfish. Microplastics are mainly found in the gastrointestinal tract in fish. This part is removed for consumption. A lot of research is still being done into the occurrence of the microplastics in the edible parts of the fish.