SOLUTION 03 / Cultivation Technology

Supporting sustainable industry to bolster food safety for the future.

Marine Farm, BIO Innovation Center
Oyster aquaculture project has started in Kunisaki City, Oita Prefecture, where fishery is facing a decrease in catch and population. Shifting to a fishery that fosters a sustainable future by realizing the methods that are well suited to the region. Aquaculture has developed into an industry that can contribute considerably to the region.


Reinvigorating Japan’s fishery industry, leveraging Yanmar technology and the vitality of private sector

Kunisaki is located on its namesake’s peninsula in Oita prefecture. The area faces the Seto Inland Sea, and its fishing community has long been largely dependent on swordfish, but recently, catches have been much reduced. This has led to a decrease in the fishery employment population, and measures were needed to save the fisheries to the next generation. In the fall of 2012, local fishermen who faced such issues reached Yanmar for consultation. Based on a plan to re-use a vacant aquaculture site, an oyster aquaculture project named Kunisaki Oysters was launched as a collaborative effort involving the local government, a fisheries association, and Yanmar. We aim to improve the Japanese fishing industry through the development of aquaculture and management methods that allow customers to enjoy the firm texture and fresh taste safely.


Growing delicious and safe oysters with a culture method unique to Kunisaki

The Kunisaki Oysters brand, grown in an area suitable for aquaculture. In pursuit of a sustainable nurturing environment and the aim of producing higher quality oysters, we thoroughly manage seeds and seedlings from the land cultivation stage to shipping. In established oyster farming regions such as Miyagi and Hiroshima, oysters are farmed by attaching the oyster larvae to a substrate formed by stringing together scallop shells and submerging them in the sea, and then moving them to areas with a high plankton density. However, Yanmar Marine Farm in Kunisaki utilizes the single-seed method in which spats or seed oysters are cultivated by distributing the oyster larvae one by one until maturation. This cultivation method, which was adopted several trials and errors, offers the following three advantages. Because the oysters move within the cage, sticking of substances that cause smell, unfavorable taste, or sea odor are not able to attach to the oysters and makes it possible to cultivate high-quality and delicious oysters. Furthermore, cage aquaculturing throughout the cultivation period reduces the number of fallen oysters that cause contaminated by marine sediment.

The second advantage is that using the "pedigreed" seed oysters produced in-house, allows thorough management of their bio-history. Cultivation using virus-free seedlings with a clear history ensures there is no adverse effect on the ecosystem. The third advantage is because most of the aquaculture process can be carefully managed, size of the meat and the shape of the shell can be modified as desired. By restricting shell growth, the proportion of meat by weight is high, and the amount of oyster husk that are thrown away is reduced.The "tidal method" that harnesses the tidal flats of Kunisaki, is also adopted. Well formed and shelled oysters are grown by changing the growth site to suit the season. In this method, high-quality production was achieved in a sustainable way that take advantage of the nature of Kunisaki. By changing the place of growth depending on the season, the oysters grow into well-formed and well-shelled oysters. The first shipments of Kunisaki Oysters, a regional specialty brand, were delivered in 2015.


Shifting from "Catching to Cultivating".

A hundred thousand oysters were sold in fiscal 2017. Sales channels have expanded with a focus on high-end restaurants and department stores. Hailed as "black gems" because of the carefully nurtured, alluring shells, raw oysters are being increasingly served in Michelin stared restaurants and popular oyster bars. Now, with Kunisaki Oysters being selected as a gift in return for "Furusato Nozei" tax donation to the Kunisaki city, the industry is contributing to regional prosperity. As an island nation, fisheries are one of the most important industries in Japan. “We feel a sense of mission as we combine Yanmar technology with private sector vitality to bolster Japan’s fishing industry. We must never allow our fishing industry to decline or become unsustainable. We want to spread the Kunisaki model,” say Yanmar employees working with the Kunisaki Oyster aquaculture project. Yanmar continues to help create a “sustainable industry” and “a future where everyone can enjoy delicious food,” by supporting this shift from wild harvesting to cultivation”.

INTERVIEWPursuing food safety through a stable production system to deliver the blessings of food to people

Enhanced safety leads to bountiful food supplies and greater nutritional flexibility. We asked Terai, who is in charge of quality control, about the strict quality control technology employed by Yanmar.

In Japan, eating cooked oysters is still prevalent, and there are people who are apprehensive about eating the oysters raw. In three years since starting shipping, "Kunisaki Oyster" has not had any food-related incident attributable to these oysters. Restaurants serving them on their menus have consistently praised the safety of Kunisaki Oysters. It is all because of the vigilant quality control technology used at Yanmar Marine Farm.

From the perspective of food safety, at present there is no technology that can purge Norovirus. In such circumstances, how to improve product safety is an important consideration. In cooperation with Oita prefecture and Kunisaki, periodic tests check whether bacteria that induce food poisoning, including Norovirus, are below the required threshold in the marine cultivation area. If the bacteria count exceeds that strict threshold, oyster harvesting is prohibited in those areas. In such restricted marine areas, harvesting can only be restarted after the cultivated oysters have been verified as thoroughly clean and safe. In addition, data gathered until now show trends, such as "these bacteria do not occur in winter." Understanding such data makes it possible to avoid areas where contamination can be predicted, resulting in improved safety.

Once the oysters are harvested they are kept in marine tanks on land, awaiting inspection. Only oysters that pass the inspection are shipped. Lastly, before shipping, the safety is further guaranteed by cleaning the oysters using the seawater that is filtered through finer than the virus size. If any negative results appear during inspection, oysters to be shipped the next day are cleansed using a purification system for around 20 hours. One oyster is capable of taking in and discharging tens of liters of seawater in one hour, washing off their bodies of bacteria. Once washed, each lot of oysters is checked for verotoxin producing bacteria such as common bacteria, E. coli, Vibrio parahaemolyticus, Norovirus, and O157. Moreover, close attention is paid to prevent oysters from possible contamination due to human contact at the last stage. Personnel having sick family members are not allowed to take in the shipping process.

Only the oysters which are verified as safe via such strict inspection and cleaning process are shipped. Of course, such diligence takes time. However, we take such care because we would like to deliver delicious oysters that customers can eat without the least concern.