TOKYO >> Making use of local hot springs, expensive tiger puffer fish are being cultivated inland, helping to revitalize local economies.

The first puffer fish cultivation project began in Tochigi Prefecture and has spread to other areas in Japan. The initial effort assembled pools in plastic greenhouses on a former swimming-pool site in Nasukarasuyama, Tochigi Prefecture. In the pools, tiger puffers, which grow to nearly 14 inches and weigh in at just over 2 pounds, swim leisurely.

Nasukarasuyama-based company Yumesozo, which cultivates the tiger puffer in water from a hot spring, launched its business in the neighboring town of Naka­gawa about 10 years ago. The company currently sells 25 tons of puffer fish a year to about 150 stores, mainly in the prefecture.

President Katsuaki Noguchi focused on the prefecture’s abundant chloride springs as a resource to develop the region, while running an environmental consulting firm in the prefecture. As he researched the composition of the hot springs’ water, he found that it contained sodium and potassium, and a salt concentration of about 1.2%, leading him to believe that the elements were right for saltwater fish to be cultivated in the hot spring water.

Tiger puffers he raised in water from a chloride spring grew faster than those raised in artificial seawater. While fish from sea farms take 1½ years to be market-ready, those grown in the hot springs reached market size in a year.

Toyoji Kaneko, a University of Tokyo professor specializing in fish physiology, told Noguchi that tiger puffer fish living in hot spring water do not burn calories to adjust the salt content in their bodies, and there is no winter chill to slow their growth.

Based on Kaneko’s theory, Noguchi also conducted research to improve the flavor of his fish. Prior to shipping, he transferred his tiger puffers from the hot springs to pools with water containing the same salt concentration as seawater. The taste of the fish improved, a result of the amino acids infused in its muscle tissue with the sudden increase in salinity.

Now, Noguchi’s company visits hot spring resorts around the country to promote tiger puffer farming. Some 18 farms have cropped up nationwide.

Kaneko believes Noguchi’s project is a great model going forward.

“On-shore aquaculture has a low risk of natural disasters. I think marine fish farming using chloride springs or artificial seawater … will spread in the future,” Kaneko said.