Breeding freshwater fish for regional specialty

Courtesy of Tochigi prefectural government

Barely cooked Premium Yashiomasu

By Naohiro Yoshida / Yomiuri Shimbun Staff WriterYamanashi and Nagano are among the landlocked prefectures successfully developing improved freshwater fish by breeding rainbow trout as well as char.

These fish have been branded and promoted as a product of the prefectures, and some are already being supplied to restaurants and receiving a positive reaction from tourists.

When I visited a fish-farming pond in Tsuru, Yamanashi Prefecture, about 8,000 fish, which were around 25 centimeters long, swam around. They were juvenile Fujinosuke, which the prefectural government raised last year by breeding king salmon, known for its tastiness, with rainbow trout, known for being easily bred.

According to Sei Yosonjo, the breeder based in the prefecture’s Fujiyoshida city, the fish currently weigh about 300 grams, but will be ready for market in about two years after growing to 3 to 4 kilograms.

“Spring water constantly flows from Mt. Fuji into the pond,” former Sei Yosonjo President Yasuhiko Sei said. “This produces a delicious product that can be eaten even as sashimi.”

At restaurants and other places within the prefecture, dishes featuring Koshu Wine Beef are popular, which is made from cattle fed the must left over during the production of wine, a local specialty. But when it comes to ayu sweetfish and other locally caught fish, stocks are limited.

Yamanashi Prefecture, however, has established advanced techniques for breeding rainbow trout in artificial fishing ponds, prompting the prefectural government to develop an original fish. In November last year, 160,000 fertilized eggs were provided to seven operators that started breeding programs.

The goal is set to start shipping Fujinosuke in 2020 when the Tokyo Olympics and Paralympics will be held. “We aim to make Fujinosuke such a well-known specialty that it will encourage people to visit Yamanashi to enjoy it,” said Masayuki Miura, a senior researcher at the Oshino branch of the prefectural fisheries technology center.

Slide 1 of 3


  • The Yomiuri Shimbun

    A Fujinosuke fish that measures about 25 centimeters

  • Courtesy of Nagano prefectural government

    Shinshu Daio Iwana

  • Courtesy of Tochigi prefectural government

    Premium Yashiomasu

While landlocked prefectures are often blessed with an abundance of local fruits, vegetables and meat products, they face problems in offering fish at restaurants and hotels. Either saltwater fish must be brought in from other prefectures, or they must use freshwater fish, for which catches are limited.

While these restaurants and hotels call for a local fish to be used on their menus, demand for conventional fish bred for use in artificial fishing ponds is decreasing, creating the need for something new. These factors have sparked the movement to develop an original freshwater fish.

The Nagano prefectural government, for its part, raised Shinshu Daio Iwana, a char that is about two times the normal size. Shipments began in 2016, and six tons were sold mainly to restaurants in the prefecture. The fish has received a favorable response, as some describe the meat as “being firm with umami,” while others say it “tastes great when marinated with miso.”

There are high expectations for the product as a brand-new fish, coming on the heels of Shinshu Salmon, a crossbreed of rainbow trout and brown trout that was first put on the market in 2004.

The Tochigi prefectural government’s Premium Yashiomasu is an improved version of its Yashiomasu, which was bred based on rainbow trout. Premium Yashiomasu is raised on special feed that has been mixed with olive oil, thus making the fish rich in oleic acid. The fish’s meat has drawn positive reviews for its rich flavor.

“It’s important [for landlocked prefectures] to raise the brand recognition not only of farmed fish, but also of their region as a whole by promoting the richness of their food derived from the blessings of nature as a selling point,” said Masaki Yamashita, chief research officer at JTB Tourism Research & Consulting Co. “It’s also vital to get tourists to visit the fish-farming ponds and allow them to sample the product nearby to convey the beauty of the breeding environment.”

To find out more about Japan’s attractions, visit


Click to play


+ -

Generating speech. Please wait...

Become a Premium Member to use this service.

Become a Premium Member to use this service.

Offline error: please try again.