TOKYO - A Japanese aquaculture firm began trial sales of the world's first fully farmed eels on Friday, a step toward fully commercializing the product amid concern over declining wild stocks.

Yamada Suisan Co., based in southwestern Japan's Oita Prefecture, released frozen grilled eel, or "kabayaki," made from eels it raised under a Fisheries Agency-commissioned project for around 4,500 yen ($28) apiece.

Most eels consumed in Japan are caught at sea early in their life cycle and raised at fish farms. Fully farmed eel production involves using eggs taken from farm-raised adults to produce the next generation, a method expected to reduce reliance on wild stocks and contribute to a sustainable supply.

But costs of fully farming eels remain three to four times higher than farming eels caught from nature.

The Japan Fisheries Research and Education Agency, which provided technological support for the project, has said costs fell from around 40,000 yen per eel in fiscal 2016 to about 1,800 yen currently by improving feed. The goal is to reduce the figure to around 800 yen.

Amid global concern over the sustainability of eel populations, the farm ministry plans to shift all eels distributed in Japan to those raised from artificially hatched juveniles by 2050.

Yamada Suisan launched the fully farmed eel product ahead of summer, when eel consumption rises in Japan, with the company seeking to determine whether consumers will accept the higher-priced products.

The product is available at Yamada Suisan's restaurant in Tokyo's Tsukiji district and through the company's official online shop, with major retailer Aeon Group also selling it online.

Shotaro Yamada, a 23-year-old graduate student from Chofu in the west of Tokyo, who began lining up outside the Tsukiji restaurant around 7 a.m. ahead of the 11 a.m. launch, said he eats eel once or twice a month.

"I am interested in how it tastes different from the eel (I usually eat)," said Yamada, adding, "I want to support the technology because it will be needed for people to keep eating eel in the future."

Related coverage: