Fish farms innovate to meet Japanese demand for bluefin tuna


For fans of Japan’s natural beauty, the subtropical island of Amami Oshima is one of the country’s brightest gems: a UNESCO World Heritage Site, southwest of the mainland in the sea between Kyushu and Okinawa, where ancient beaches merge with dense mangrove forests.

But, over the past 35 years, the tiny archipelago has also been a testing ground for one of food production’s most complex, frustrating and ambitious sustainability challenges: the quest to produce Pacific bluefin tuna. from egg to full-scale commercial harvest. .

The mission involves two distinct sustainability issues, two sides of the same fundamental problem that the fish itself is delicious and that human appetites threaten its long-term survival. Overseas imports to meet Japanese demand for fish have a large carbon footprint, but the main alternative – domestic fish farms – require large quantities of fishmeal, which also poses sustainability issues.

These problems, and the possible solution, took years to develop. Japan’s diet changed dramatically from the 1970s, as the country went through its “economic miracle” phase of growth and a large, wealthy, consumerist middle class emerged.

Japan’s historical reliance on fish as a key source of protein has evolved, due to its wealth and global economic reach, into a national obsession with acquiring the best seafood on the planet. . Over time, and with the powerful Japanese trading houses as the main enablers, fish and seafood imports have occupied an increasingly larger proportion of the total consumed in Japan – it currently stands at around 40%. Among the best countries in the world in terms of GDP, Japan remains the largest consumer of fish and seafood per capita.

All of the CO₂ emissions associated with the large volume of imports could be reduced if Japan shifted its consumption towards domestically farmed fish. But the problem, according to one of the country’s largest fishing companies, Maruha Nichiro, is that Japanese fish farming in its current form requires between 2.5 kg and 3.5 kg of fishmeal to produce every 1 kg of fish. aquaculture fish, which is inefficient compared to fish farming. somewhere else.

In Norway, for example, known for salmon farming, 1 kg of fishmeal produces 1 kg of salmon, says Tsutomu Watanabe, who oversees fish farming at Maruha.

“We need more research and development for farming that not only requires less fishmeal, but also makes the fish less likely to get sick and yields more meat from the body,” says Watanabe. This fishmeal would ideally be replaced with soy or corn based foods.

In its great love of fish, Japan’s fondness for prized Pacific bluefin tuna – a key ingredient in sushi and sashimi cuisines – has been particularly voracious. This has resulted in a significant decrease in the natural fish population and the species appearing on the International Union for Conservation of Nature’s “Red List” of Near Threatened Species.

As this decline has deepened, it has raised the question of whether Japan’s love for bluefin tuna is sustainable – and whether it could be by mastering the notoriously difficult task of rearing tuna through a full life cycle in captivity.

The first private company to devote serious resources to the project was Maruha. Others have made progress, but not on this scale. One is Toyota Tsusho, the trading arm of the Japanese automaker, which began working with Kindai University in 2010 to develop fully-farmed bluefin tuna and began exporting in 2017.

Maruha, who recognized looming sustainability issues years ago and set aside the Amami Oshima facility to tackle the task, began work on developing a tuna farm in 1987 , but abandoned the project a decade later after persistent failure.

A separate breakthrough at Kindai University in 2002 prompted Maruha to resume his efforts after a nearly decade-long hiatus in 2006, but this time with the cooperation of six academic institutions in what had effectively become a national effort. .

The difficulties related to the extreme fragility and environmental sensitivity of newly fertilized bluefin tuna eggs, the high mortality of larvae and the non-negotiability of their diet. Gradually, and over years of trial and error, techniques have been improved and ever larger batches have been brought in of the eggs at the age of three and a half where they can be eaten.

In 2015, Maruha’s two farms in Amami Oshima were able to make the company’s first commercially viable shipment to sushi chefs in Japan, and by 2019 they were producing enough to sell captive-bred bluefin tuna in Europe.

In the fiscal year from April 2020 to March 2021, Maruha produced 500 tonnes of bluefin tuna in a closed cycle environment, but this only covers 15% of its overall fish sales. The company’s objective is that all of its bluefin tuna come from closed cycle farms.

However, as the absolute level of fully high bluefin tuna production increases, so does the power of the second sustainability challenge. It takes three and a half years for farmed bluefin tuna to hit the table, and they not only consume a huge amount of food, but are currently restricted to a diet that depends on wild fish.

To make the operation more sustainable, says Maruha, research needs to focus on finding a way to farm bluefin tuna on alternative plant proteins, keeping the fish healthy but also retaining its flavor.

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