Water from Deep Underground Supports Flounder Farming in Aomori; Climate Change Pushes Prefecture’s Marine Industry to Switch from Fishing to Aquaculture

By Hikari Yadaka / Yomiuri Shimbun Staff Writer

12:06 JST, September 22, 2025

SOTOGAHAMA, Aomori — On Cape Tappi, the northern tip of Aomori Prefecture’s Tsugaru Peninsula, water that seeps through the rocks of the undersea Seikan Tunnel is now being used to farm high-quality Matsukawagarei Barfin flounder.

Since the water is pumped up from underground, it is less susceptible to high water temperatures, which can cause poor aquaculture harvests. An increasing number of fishers and others related to marine industries are taking up Barfin flounder aquaculture, as well as collaborating with various organizations to develop their businesses and increase their name recognition.

At an aquaculture facility in Sotogahama, Aomori Prefecture, near Cape Tappi, black Barfin flounder were swimming energetically, occasionally jumping out of the water. Akina Ito, 42, president of Lalaki, the seafood processing company that operates the farm, said, “Our strength is the water. Anyone who tries our fish is sure to become a frequent customer.” The company ships approximately 13,000 of the fish, labeled “Tappi Misaki Matsukawa,” to restaurants within the prefecture and in Tokyo each year.

A continuous flow system supplies water to aquaculture farms by pumping it up from 200 meters below sea level, where it seeps through rocks into the Seikan Tunnel that connects Honshu to Hokkaido. The water temperature remains stable at around 18 C year-round, which is said to make the fish swim more actively, giving their meat a firm texture. The water itself is moderately filtered, preventing odor and lowering the risk of parasites such as anisakis.

Ito, a native of the town, said, “First, I want local people to become aware of it, and eventually, I aim to make it a big brand name, like Hokkaido’s ‘Ouchou’ [“king flounder,” a local variety of Barfin flounder].”

The prefecture’s fishing industry now faces significant challenges due to changes in the marine environment, such as a decline in scallop production caused by high water temperatures. In response, the prefecture is promoting a shift from marine industries based on catching fish and marine life to ones based on cultivating it. The prefectural aquaculture promotion association in Hashikami, Aomori Prefecture, began raising Barfin flounder from eggs to fry in 2023 with the support of the prefecture.

Once the fry reach a certain size, they are raised at Ito’s aquaculture facility on Cape Tappi, as well as experimental aquaculture facilities in the town of Nakadomari and the village of Sai, both in the prefecture.

Barfin flounder fetch high prices and are considered relatively easy to raise, as they are resistant to oxygen deficiency and disease. While high water temperatures remain a challenge for aquaculture outside of Cape Tappi, a growing number of people involved in marine industries are making efforts to raise Barfin flounder from fry obtained from facilities like these.

In June, the prefectural aquaculture promotion association, along with universities, research institutions and marine industry members, established the prefectural Matsukawa aquaculture promotion council, aiming to expand aquaculture and raise awareness of Barfin flounder.

“Through this council, we hope to create synergies; solve issues related to production costs and water temperature; and accelerate the commercialization of Barfin flounder aquaculture,” said the council’s chairman.