Unlocking the Future of Food with Cutting-Edge Land-Based Aquaculture

Recreating the Environment of Tidal Flats and Shorelines

Tokyo Bay was once known as an abundant fishing ground, with seaweed farming in the coastal areas, since the Edo Period (1603-1868). Fishing in the bay gradually declined, however, due to land reclamation projects during Japan's high-growth post-war period, and later, due to a deterioration in water quality. Nowadays, most of the fishing occurs around the Tokyo Islands, located outside the bay. With fishery production declining not only in Tokyo but across Japan, a new kind of fishery industry has emerged into the spotlight—land-based aquaculture, a form of aquaculture that does not require the ocean, and can be implemented even in mountainous and urban areas.

WithAQua, headquartered in Shinagawa City, Tokyo, is gaining noteworthy recognition for the novel system they have come up with to solve the issues that arise in aquaculture.

One method of land-based aquaculture that has attracting attention is known as "land-based closed-containment aquaculture," in which fish are cultivated in water that is circulated and filtered. The issue with this method, however, is water quality. For instance, take the ammonia that the fish themselves produce. Biological filtration can be used to convert ammonia into nitric acid to dampen its effects on water quality. However, even nitric acid can damage the organs of fish if it accumulates, causing indigestion and other issues that can lead to illness. Removing this nitric acid is quite difficult to do using technology, and this posed a major issue in land-based aquaculture. In order to get past this obstacle, withAQua has implemented a new technology called aerobic denitrification.

"After graduating from the Tokyo University of Marine Science and Technology (TUMSAT), I worked for a pearl farming business for a while, then went back to get my doctorate. After this, I went and applied the aerobic denitrification technology (patented by the TUMSAT) invented by Professor Endo Makoto (currently professor emeritus at the TUMSAT)—my advisor at the time and the company's current technical advisor—to pearl farming. I found that this dramatically improved the health of the Akoya pearl oysters I tested it on. I set up the company in 2019 so that I could promote this ground-breaking new technology to the rest of the world, and put it to good use," says Ogimura Tohru, executive director of withAQua.

Land-based aquaculture typically utilizes anaerobic denitrification. This method relies on anaerobic bacteria, which do not require oxygen, to break down nitric acid and release it into the atmosphere. However, these systems are complex and require large amounts of space, meaning that they take a very long time to set up. Enter Professor Emeritus Endo's invention—the aerobic denitrification device—which allows nitric acid to be removed in a simple, safe manner.

Ogimura says, "The aerobic denitrification device creates an environment similar to that of tidal flats and shorelines, where aerobic bacteria—which use oxygen to decompose nitric acid—are found. We regularly raise and lower the water levels in the tank to expose the bacteria to the atmosphere and provide them with the oxygen they need."

Helping Reduce Food Loss While Maintaining Quality

The aerobic denitrification device only takes a few days to set up and is highly effective, meaning it can be installed on a small scale, and at low cost. It is also risk-free and easy to maintain. The device is combined with a biological filtration tank and a protein skimmer that uses bubbles to remove water-soluble proteins and particulates, to create a completely closed, land-based aquaculture system. Ogimura says that the water in the tanks is as clean as water from the deep sea.

"The water the fish are cultivated in is clean, meaning they're also very safe to eat. They don't get harmful parasites and microorganisms because we use artificial seawater. The system also helps limit illness. Typically, when fish are grown in tanks, the odors caused by bacteria in the tank can seep into the fish. But this system has very little bacteria content and is almost odorless. The high water quality means fish grow faster, and can be shipped out in about six months. They also look very good, particularly fins. We did a taste test of farmed flatfish with chefs in Ginza, an area of Tokyo where there are a lot of very high-end restaurants. We were told that they were of good enough quality to be used in Ginza's sushi restaurants. We've also managed to cultivate healthy abalones and Japanese spiny lobsters, which are typically difficult to keep long term," says Ogimura.

With the addition of the aerobic denitrification device, the technology for land-based aquaculture is now ready. High costs, however, remain an issue, with Ogimura making various efforts to resolve it. If this method were to be implemented, live fish caught at sea could be transported inland, and kept in a healthy condition. The ability to "stock" live fish would allow for an environment in which fish could be supplied in only the quantities necessary, which could help reduce food loss. The system, if introduced in the underground spaces of Tokyo, where there is little fluctuation in temperature, would also allow restaurants in central Tokyo to be supplied with fresher fish than ever before.

"We're still in the experimental phase now, but we're of course considering implementing aerobic denitrification for general use, and also utilizing it for research and education purposes. It'd be great if in the future, this technology could be used across the world so that you could have access to delicious seafood anywhere," says Ogimura. A Tokyo-based innovation, spread throughout the world, could revolutionize food-related challenges in various countries and help improve the global environment. The future developments of this amazing new system will be exciting indeed.