By The Japan News
Asia News Network
Inland cultivation of expensive tiger puffer fish has spread from Tochigi Prefecture to other areas in Japan, helping revitalize local economies.
Intensive research was undertaken to make use of local hot springs.
Cultivation pools have been set up in plastic greenhouses on a former swimming pool site in Nasukarasuyama, Tochigi Prefecture. In the pools, tiger puffers, which grow to about 35 centimeters in length and one kilogram in weight, swim smoothly.
Nasukarasuyama-based company Yumesozo, which cultivates 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, 62, 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 elements including sodium and potassium, and its salt concentration was about 1.2 percent.
Living cells’ salinity is about 0.9 percent, about the same as saline solutions used for medical purposes. Fish living in seawater with a salinity of about 3.5 percent excrete excess salt from their gills. Noguchi thought saltwater fish could be cultivated in the hot spring water.
Tiger puffers he raised in water from a chloride spring grew as well as in artificial seawater. Although it takes 1½ years for fish raised in sea farms to be ready for market, those grown in the hot spring water reached market size in one year.
Toyoji Kaneko, 62, a University of Tokyo professor specializing in fish physiology, told Noguchi that tiger puffer fish living in hot spring water do not need to burn calories to adjust the salt content in their bodies, and there is no winter chill to also slow down their growth.
Based on Kaneko’s theory, Noguchi also conducted research to improve the taste of tiger puffer. He used a technique to transfer tiger puffer from a hot spring to a pool of water with the same salt concentration as seawater, before the fish’s shipment. Noguchi confirmed that tiger puffer’s taste improves when it injects amino acids into its muscle tissue to cope with the rapid change of osmotic pressure caused by the sudden increase in salinity, as it had been accustomed to the lower salt concentration of the chloride spring.
When requested, the company visits hot spring resorts around the country to promote tiger puffer farming. There are already 18 sorts of “local hot spring tiger puffers” nationwide. “On-shore aquaculture has a low risk of natural disasters. I think marine fish farming using chloride springs or artificial seawater with a low salt concentration will spread in the future,” Kaneko said.