The following is the sixth installment in the third section of the "Creative use of land" part of a series of articles examining ways to restore Japan's vitality after the March 11, 2011, disaster.

This section examines how land should be used and maintained.

A "fish factory" has been in operation for two years on the hilly campus of Okayama University of Science in Okayama.

The indoor facility is equipped with water-circulation machines and other devices.

The project is one of an increasing number of attempts to introduce the latest science and technology into primary industries to make the field more profitable.

The one-story building holds large and small aquarium tanks, including a round tank measuring eight meters in diameter near one end of the building, where three bluefin tuna, each weighing about eight kilograms, were swimming around.

Toshimasa Yamamoto, 53, an associate professor of the university's Faculty of Engineering, said: "I want to establish technologies to enable fish farming with high added value even in villages in mountainous regions where depopulation or graying of the population is progressing. By doing so, I want to create new industries."

He developed a method of adding small quantities of sodium, potassium and other elements to freshwater so that both saltwater fish and freshwater fish can be farmed in it.

The method is less costly than transporting seawater to mountainous areas and makes it easier to control water quality.

Currently, the fish-farming research is under way with eight species of fish.

Yamamoto has especially high hopes for bluefin tuna, which are high-quality fish.

Farming bluefin tuna is difficult because the fish swim at high speeds, and are sensitive to light and sounds. Often the fish crash into tank walls or jump out of the tank.

In 2010, when he first got the fish factory running, all the tuna died. Since summer of last year, he has made some improvements to the facility.

For example, iodine, which has bactericidal effects, has been added to the water, and nets to prevent fish from jumping out have been placed over the tank.

As a result, young 25-centimeter fish have grown to 80 centimeters in eight months.

An official of Okayama Takashimaya department store, which bought 200 tiger puffer fish from the fish factory for year-end seasonal gifts, said: "The taste is as good as normally farmed ones. As it is a technology with great future potential, I wanted to strike deals quickly."

If costs for circulating and purifying water can be lowered, the fish will be more competitive in the market.

Yamamoto has received proposals for joint research from US, Chinese and South Korean companies.

He said, "An age in which agricultural cooperatives will ship bluefin tuna may be coming."

Vegetable factories are also attracting attention.

These bio-factories produce agricultural products by artificially controlling temperature, water conditions, nutritional elements and other factors indoors.