A bluefin tuna caught near Maine, U.S., in 2018 (AP Photo/Robert F. Bukaty, File)
A Spanish research institution has succeeded in doing this, but there are concerns about the impact on the environment and fish welfare
Last July, the Spanish Institute of Oceanography (IEO) announced that, for the first time in the world, it had succeeded in breeding bluefin tuna in captivity in a land-based aquaculture facility. This success of the research center immediately aroused the interest of some companies who, in collaboration with the IEO, are organizing the opening of the first large land-based bluefin tuna farms.
In fact, bluefin tuna meat is in high demand, but catching and farming this fish in the sea has a major impact on the environment: the possibility of farming it “on land” could make the sector more sustainable. However, there are also voices that believe that such aquaculture could be more harmful than current methods, including for the well-being of tuna, which as adults can be more than two meters long and weigh several hundred kilos and in nature they move Thousands of kilometers in the ocean.
Bluefin tuna is one of the different species of tuna that exists in the world and is found in the Atlantic Ocean and the Mediterranean Sea: its scientific name is Thunnus thynnus and it is also called “bluefin tuna”. It is not one of the tuna species whose meat is sold canned (these are skipjack tuna, yellowfin tuna and bigeye tuna, economically cheaper and considered less valuable), but it is one of the three species from which sushi and tuna sashimi are made become . The others are the Pacific tuna (Thunnus orientalis), which, as the name suggests, lives in the Pacific Ocean, and the southern tuna (Thunnus maccoyii), which lives in a very southern band of the world’s oceans almost to the limits of the Southern Ocean : Externally, these two species are practically indistinguishable from bluefin tuna and also have red-colored flesh.
Most of the bluefin tuna of the three species consumed worldwide is fished, although in recent years a form of farming based on the fattening technique has become widespread: young free tuna are caught and bred in large nets in the sea until they arrive at the right size, to be sold on the market. Since 2015, a second form of aquaculture, which is currently still in the minority, has been added to this form of aquaculture. This year, the Japanese company Maruha Nichiro sold the first Pacific tuna that it had bred from birth, first in aquaculture facilities on land and then in nets at sea: by adding a certain amount of hormones, it was possible to keep the fish in captivity reproduce in the pools in which the adults swam and were thus urged to produce and fertilize eggs.
The Spanish Institute of Oceanography is the first institution to have succeeded in doing the same with Thunnus thynnus, the bluefin tuna of the Atlantic and Mediterranean, and two European companies, the German Next Tuna and the Norwegian Nortuna, are working on producing it Scaly tuna aquaculture with its methods. Next, Tuna wants to build a facility near Valencia, Spain, while Nortuna wants to build in Cape Verde, West Africa.
Although this type of aquaculture is still in its infancy, it has attracted great interest as the way tuna fishing is conducted is considered unsustainable for the conservation of the species.
Japan is the largest importer of all three bluefin tuna species and the world’s largest consumer, followed by the United States, where an estimated 8 to 10 percent of the world’s sashimi is eaten. In the last decades of the 20th century, large demand from Japan and the United States significantly reduced the amount of bluefin tuna of these three species, although catch limits introduced around 2010 improved the situation. According to estimates by the International Union for Conservation of Nature (IUCN), the United Nations-recognized organization that assesses which animal and plant species are at risk of extinction, the southern tuna is still at risk of extinction and the Pacific tuna is threatened.
Instead, the bluefin tuna (which lives in the Atlantic and Mediterranean) is no longer considered threatened because, although the population in the western Atlantic declined by 83 percent between 1966 and 2018 due to overfishing, it is estimated that the bluefin tuna in the eastern Atlantic, their population represent the clear majority overall, have become more numerous since the 1960s until today. However, concerns remain about the sustainability of the fishery due to population decline in the West.
For companies engaged in or interested in pursuing bluefin tuna aquaculture, the use of techniques that allow fish to reproduce in captivity would reduce pressure on wild populations and should therefore be preferred. To keep tuna at breeding age in tanks on land, you need to be able to regulate both the water temperature and the lighting. In this way, according to those involved in the aquaculture project, it will be possible to extend the period of the year in which bluefin tuna can reproduce. In nature they do this for about 45 days between June and July. If they do it longer in farms, they maintain larger populations in captivity than those who are fattened after catching young tuna in the sea.
However, some scientists have raised concerns about the new form of farming, involving both animal welfare and the environmental impact the sector could develop.
As for tuna directly, the Spanish animal protection organization Observatorio de Bienestar Animal considers that even very large and spacious tanks are not a suitable environment for the needs of a migratory species such as the bluefin tuna, which travels thousands of kilometers in search of food to reproduce.
In an article published in The Conversation, Wasseem Emam, a researcher at the Institute of Aquaculture at the University of Stirling, explained that it is difficult to assess the life experience of tuna in tanks because the companies that have tuna do not spread too much information about it . But “in general, non-domesticated fish species experience greater stress in captivity and when interacting with humans than species that have adapted to breeding over time.” Emam also cites some studies that suggest that fish are affected by noise and certain vibrations likely to occur in land-based breeding facilities. However, it would be in the interest of farmers to avoid this stress as it is known that the meat of stressed fish is of lower quality. In particular, bluefin tuna’s body is known to produce large amounts of lactic acid when it tries to escape before it is killed, which worsens the taste of its meat.
Adding to concerns about the tuna’s welfare are concerns about the environmental impact and sustainability of large land farms. The first is related to the feeding of tuna in captivity: currently, fattened bluefin tunas are largely fed with species of fish that could also be used in human food, and in Japan it takes between 2.5 and 3.5 kilos to produce 1 kilogram of farmed Pacific tuna meat other fish. This also means that fishing for other species would have to be increased in order to farm tuna in large quantities on land.
Maruha Nichiro conducts research to improve the efficiency of feeding tuna in captivity. Nortuna’s president, Anders Attramadal, instead downplayed this issue when speaking to the Guardian, claiming that land-raised tuna eat less than sea-raised tuna; Andrew Eckhardt of Next Tuna said instead that his company will try to reduce the amount of fish needed to feed tuna by making feed based on other ingredients such as plant proteins, algae and insects.
Other concerns include the use of antibiotics that will be required on farms to prevent the spread of disease (very common in all types of industrial livestock farming) and water pollution from discharges from aquaculture facilities. Next, Tuna says he doesn’t want to use antibiotics, and Nortuna says he will use them minimally. With water pollution in mind, the first company is designing a system to collect seawater but not release it back into the sea. Neither the details of the Next Tuna nor the Nortuna factory are currently known. When it comes to Pacific tuna, Maruha Nichiro takes a different approach: As soon as the fish in the tanks on land have reached a certain size, he transfers them to nets in the sea.
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