The story of bluefin tuna: Cat food turned high-end delicacy
An in-depth look at ranching and farming the cattle of the deep — can we sustain our appetite for tuna?
Ranching. The term conjures up images of cowboys with boots and spurs, swinging lassos, thundering through the dust as they round up cattle. But far from the dusty plains, in the cold depths of the ocean, a different type of stock is being rounded up: tuna.
Tuna schools are encircled by boats, corralled into nets and herded into pontoons that are slowly towed to the coast, where the tuna are transferred into offshore farms to be fattened up over the next 8 months to 2 years¹.
Tuna ranching is big business. Tens of thousands of tonnes per year of tuna come to market from tuna ranches all over the world¹. Most ranched tuna is bluefin tuna, though some yellowfin is also produced this way. This tuna is almost exclusively sold in high-end markets as fresh fish for sushi or the like, it is rarely destined for tins.
The record price for tuna is $11,000 USD/kg. ²
The story of bluefin tuna and sushi is a story of rags to riches, that collided head-long with modern consumerism. Around the world, bluefin tuna was not always a prized delicacy — it was a pest. In Japan, historically, fish with white flesh were more highly prized for sushi, not tuna with its striking red-flesh. The same was true in the Mediterranean where the abundant Atlantic bluefin was rarely, with the exception of Sicily where it was a feature of many dishes associated with the poor³. Bluefin was relegated to pet food.
It was not until the 1960s that bluefin tuna began to appear in Japanese cuisine. Even then, bluefin belly (maguro toro as it is called in Japanese) was discarded and given to cats³. This all changed in the 70s-80s. From previous obscurity its uniqueness led to it becoming a status symbol of the wealthy and the price of bluefin skyrocketed by 10,000%³. This coincided with a growing economy. More people could afford more luxuries and the demand opened a market for lower grade bluefin that was accessible to the masses. Suddenly this former pest was the biggest prize of the ocean and populations plummeted, further fuelling the glamour and appeal of this dwindling resource.
Tuna ranching was the answer to the crashing bluefin populations. On the surface, at least, this practice seems like a win for sustainability. It allows us to get more value out of each individual tuna we catch and allows the fishing industry to operate despite tightened fishing quotas.
The key to remember here, is that tuna ranching is not true farming; the fish do not breed in captivity. This is both its greatest strength and its greatest weakness.
As the fish are wild-caught, they tend to carry few diseases⁴ ⁵. Domesticated animals are plagued by diseases because they are selectively bred. They are often so similar genetically, that they lack unique genes that offer individual protection so diseases can rip through the entire population. Catching and ranching wild fish avoids this problem. Being older when they reach the farm, these fish normally have more fully developed immune systems, those who don’t rarely surviving long in the wild⁴. Transmission of diseases between catches is avoided by fully emptying enclosures before new stock is introduced⁴ ⁵. The low-rate of disease and unaltered genetics removes many of the problems regarding fish escapes that are of high concern for ecosystems in areas with truly domesticated fish farms, such as salmon farms. However, these are wild fish and they are critically endangered. Even if tuna ranching does decreases the number of fish we take, it does not completely remove pressure from the ecosystem.
Biology is complicated. Bluefin tuna is not a single species — there are three: the Pacific, the Southern and the Atlantic. These are not only found in different tracts of the ocean but they also have different requirements for reproduction and mature at different rates. The Pacific species begins spawning at 3–5 years⁶, the Atlantic at 4–8⁷ and the Southern bluefin at 8–14 years¹ ⁵. These are huge differences to consider when determining policies for sustainability. All bluefin ranching operations worldwide are able to take, and generally try to target, smaller fish that have not yet reached sexual maturity. The size taken ranges worldwide; Japan takes the smallest fish of 100–2000 g¹ ⁶, Croatia targets 8–10 kg and other Mediterranean countries 30 kg⁷. These fish are effectively removed from the breeding cycle. They do not breed in captivity so they do not contribute towards securing the next generation.
Unfortunately, despite its potential, this practice has historically depleted populations rather than restored them. Ranching would have be fine on a small-scale but as the tuna ranching industry developed there was corresponding boom in aircraft and refrigeration technology, allowing the rapid transport of fresh fish around the world³. The industry was so successful, so lucrative that even countries not traditionally involved in tuna fishing entered into business. The impacts were severe in the Mediterranean.
Built on top of an already prolific fishing industry with lagging regulations and inadequate enforcement, there was a rapid demise in the overall population of Atlantic Bluefin. Traditional small-scale tonnoro fisheries in Sicily collapsed to be replaced by multinational giants³. The speed of technological change left the system open for exploitation. Inaccurate reporting and loopholes regarding documentation needed when trading live tuna were used to blur catch sizes⁴ ⁸.
There have since been changes in regulations and monitoring and these have pulled populations back from the brink. Catch sizes are more carefully monitored, with cameras used to determine the size and number of fish released into farms and full documentation is now required⁹. Due to this Atlantic bluefin populations have somewhat recovered, though they are still endangered¹⁰. However, this highlights the speed with which industries and entire ecosystems can shift and veer towards collapse
This brings us to the future. We must keep abreast of technological advancements. Even the most sustainable solutions can only eventuate with adequate regulation, enforcement, research and communication.
The single biggest hurdle for ranching and the future of tuna populations is the development of fish feed. Tuna are natural free-rangers, covering up to 260 km in a day and 94,000 in a year¹¹. This marathon effort requires a lot of energy. Additionally, tuna are unusual among fish in that they actively maintain a high body temperature. As a consequence, they require a lot of food. Production of one pound of tuna takes between 8–30 pounds of feed, depending on climate, species and the food provided⁷ ¹².
Food in aquaculture is the subject of intensive research. Ranched tuna are fed squid as well as smaller fish like sardines. These are themselves caught and transported to the tuna farms, putting pressure on lower rungs of the food chain. There are also further complexities, such as fluctuations in these feed populations and the nutrition they contain, as well as transport, logistics and bio-security considerations. Feeds are increasingly supplemented with ingredients like soy and additional vitamins to reduce reliance on these other fish but they have not been fully eliminated. Decoupling aquaculture from its reliance on fish feed stocks is likely one of the essential changes needed to secure sustainable sources of seafood for consumption over the next two decades (See my previous post on this). Insects, yeast and algae offer possible solutions. This industry cannot be continuously increased to respond to future human population increases with the current reliance on other fish stocks as feed. But we also can not expect wild populations to cope with these demands.
Assuming that we are able to resolve the feed limitations, the often lauded ‘golden ticket’ for sustainability and supposed future of the industry is to transition to true ‘egg-to-adult’ tuna farming. This would radically decrease the fishing pressure on wild stocks, while securing tuna to match global demands as the human population increases. But is this truly a viable alternative?
Essentially, we are looking to domesticate the tuna, producing a species that we can be easily and quickly breed in captivity. There are significant challenges here though, due to tuna’s biology.
In the wild, the tiny transparent 2mm long fingerlings float across the great expanse of the ocean, dodging the monsters of the deep. In the lab, like some nightmarish family reunion, they are surrounded by their siblings — their ravenously hungry siblings, with nowhere to escape. Cannibalism is a major problem and up to half of the baby tuna can end up as snacks for their peers⁵. Once the fish are old enough to start schooling, i.e. swimming in a coordinated group, cannibalism reduces and a new problem emerges. As residents of the open ocean, they simply lack the motor skills to navigate in such confines. The young tuna collide with the tank walls, suffering fatal injuries. Measures taken to reduce the risks include lining the walls with safety nets and controlling the environment to prevent alarming the fish in any way⁵ ⁶.
With all of these technical limitations, full-cycle farming of tuna has not been wildly successful. There have been many companies interested in this in passing, though a number of Mediterranean and southern Australian companies seem to have put their research and investment on hold for the time being, focussing on other, more amenable fish species, though significant advancements have been made. Kindae (formally Kinki) University in Japan has seen the most success. And indeed, full-cycle tuna is now regularly sold and eaten in Japan but it is only regarded as mid-range tuna, so is unlikely to ever fully replace wild-caught tuna on sashimi menus.
The success of full-cycle farming may also be a double-edged sword. Current extreme tuna prices are driven by shortages in the wild population, which will decrease with increased tuna supply. Full-cycle farming is costly, so high tuna prices are essential to balance costs, though the increased global interest and uptake of sushi worldwide may compensate for some losses here.
Continued adjustments of regulations, enforcement, monitoring technologies and the further introduction of marine reserves will be essential to the long-term sustainability of tuna but history shows that these alone will not be enough. Advancements in feed technology will be absolutely critical as to whether the industry can keep pace with future demand, as will regulations that keep speed with these advancements.
The truth is tuna is not a sustainable farming dream. It is difficult and resource intensive. There are other alternatives we should and could be turning to. That tin of tuna on the shelf? It is a sustainable superstar in comparison to fresh tuna steak.
Skipjack tuna is most commonly in tins and, at least for now, it is not showing signs of over-fishing. Though it may not seem like a premium product, tins store the product long-term reducing food wastage, they are easy to transport en masse — no refrigeration needed, drastically reducing the carbon footprint (oh, and the tins are recyclable!). If you need more convincing on why you should re-evaluate tinned fish see this great blog post.
For myself, I am not entirely conformable with relying on technology to catch up, especially with the compiling impacts on the broader ecosystem. Perhaps, ultimately, we should again change what we view as premium. Let’s place the premium label on fish that truly reflect this claim — high nutrient, low contaminant, ecologically sustainable. These labels belong to the sardines, mackerel and herring that, ironically, we use to feed these tuna. Let’s celebrate these fish, that are largely affordable and accessible to all and can be into the future. For some inspiration here is a blog post with some recipes to get you going.
If you would like to know more about tuna, how it is caught and the best tinned tuna choices see my previous post:
References
¹ Peng, S., Wang, L., Wang, Y., Zheng, H., Min, M., & Shi, Z. (2019). Research Progress on Artificial Culture and Breeding of Tuna in the World. https://doi.org/10.12677/OJFR.2019.63025
² Elassae, A. (2019) Massive tuna nets $3.1 million at Japanese auction, https://edition.cnn.com/2019/01/05/asia/giant-tuna-sets-record-at-japan-auction/index.html, viewed 12 February, 2021
³ Longo, S. B. (2011). Global Sushi: The Political Economy of the Mediterranian Bluefin Tuna Fishery in the Modern Era. Journal of world-systems research, 403–427. https://doi.org/10.5195/jwsr.2011.422
⁴ Karakulak, F. S., Öztürk, B., & Yıldız, T. (2016). From ocean to farm: capture-based aquaculture of bluefin tuna in the eastern Mediterranean Sea. In Advances in Tuna Aquaculture (pp. 59–76). Academic Press. https://doi.org/10.1016/B978-0-12-411459-3.00020-5
⁵ Chen, B. N., Hutchinson, W., & Foster, C. (2016). Southern bluefin tuna captive breeding in Australia. In Advances in Tuna Aquaculture (pp. 233–252). Academic Press. https://doi.org/10.1016/B978-0-12-411459-3.00009-6
⁶ Buentello, A., Seoka, M., Kato, K., & Partridge, G. J. (2016). Tuna farming in Japan and Mexico. In Advances in Tuna Aquaculture (pp. 189–215). Academic Press. https://doi.org/10.1016/B978-0-12-411459-3.00007-2
⁷ Mrčelić, G. J., Miletić, I., Piria, M., Grgičević, A., & Slišković, M. (2020). The Peculiarities and Farming Challenges of Atlantic Bluefin Tuna (Thunnus thynnus, L. 1758). Croatian Journal of Fisheries, 78(1), 33–44. https://doi.org/10.2478/cjf-2020-0004
⁸ Benetti, D. D., Partridge, G. J., & Stieglitz, J. (2016). Overview on status and technological advances in tuna aquaculture around the world. In Advances in tuna aquaculture (pp. 1–19). Academic Press. https://doi.org/10.1016/B978-0-12-411459-3.00001-1
⁹ van Beijnen, J. (2017). The closed cycle aquaculture of Atlantic Bluefin Tuna in Europe: current status, market perceptions and future perspectives. https://doi.org/10.13140/RG.2.2.14033.53601
¹⁰ World Wildlife Fund (2021) Bluefin Tuna, https://www.worldwildlife.org/species/bluefin-tuna, viewed 12 February, 2021
¹¹ Wardle, C. S., Videler, J. J., Arimoto, T., Franco, J. M., & He, P. (1989). The muscle twitch and the maximum swimming speed of giant bluefin tuna, Thunnus thynnus L. Journal of fish biology, 35(1), 129–137. https://doi.org/10.1111/j.1095-8649.1989.tb03399.x
¹² Ottolenghi, F., Silvestri, C., Giordano, P., Lovatelli, A., & New, M. B. (2004). Capture-based aquaculture: the fattening of eels, groupers, tunas and yellowtails. FAO.
