October 28, 2025
TOKYO – Tokyo will begin producing locally farmed caviar on Kozushima Island amid the decline in the number of spiny lobsters.
The Tokyo metropolitan government aims to cultivate sterlet sturgeon, which produces roe used to make caviar, creating a new income source for local fishermen. The caviar is expected to be on sale in jars and other forms by fiscal 2030.
Kozushima, in the Izu Islands, is located 160 kilometers southwest of Haneda Airport, and 50 kilometers south of the Izu Peninsula in Shizuoka Prefecture. The island, with a population of 1,719 as of Oct. 1, is known for its set net fishing of spiny lobster and pole-and-line fishing for red seabream. However, the catch of spiny lobster has declined by 98% over the past 40 years.
A sterlet sturgeon planned for aquaculture by the Tokyo metropolitan government and the Kozushima municipal government. PHOTO: FUJIKIN INC./THE YOMIURI SHIMBUN
“In the past, most boats focused on fishing for spiny lobster, but now there are only one or two left,” said Yoshiki Maeda, 63, chairman of the Kozushima fisheries cooperative.
The catch, which exceeded 23 tons in 1986, plummeted to 7.6 tons in 2013 and then to just 0.4 tons in 2023. Maeda said that in recent years the catch has been “at best about 10 kilograms per day.”
A 300-square-meter tank facility sits near the port in the eastern part of the island. When there is a good catch, some spiny lobsters can be stored here to prevent price collapses from simultaneous shipments. However, it has hardly been used in recent years and remains unfilled with seawater even during the fishing season from November to March.
According to the metropolitan government, the long-term decline in catches is thought to have been factors such as a result of rising sea temperatures due to global warming. The number of shellfish, such as abalone, and seaweed has also decreased. The number of fishermen has also fallen, from 182 in 2013 to 137 in 2023, a 25% drop over a decade.
As a result, Tokyo and the village of Kozushima have turned their focus to aquaculture, which is less susceptible to rising sea temperatures. After researching various fish species with a high value, they settled on freshwater sturgeon. They thought that the abundance of spring water was ideal for the freshwater fish, along with the lobster tanks.
Last month, Tokyo and the village signed an agreement to cooperate on aquaculture. The metropolitan government would cover the costs of research and for the renovation of the tank facility, which would need to be modified for sturgeon cultivation, while village will advance commercialization of the caviar for fish meat products.
“We can reuse the tanks to farm sturgeon,” said Maeda. “This is a welcome initiative.”
Juvenile and adult fish will be put into the tanks from next fiscal year, and a production system will be established by as early as fiscal 2030.
“After achieving success on Kozushima, we want to expand land-based aquaculture to areas like the Tama region and advance the branding of ‘Tokyo Caviar,’” a metropolitan official said.
Possible effects of global warming
The fishing industry in other areas of Japan has also seemingly been affected by global warming, with some municipalities collaborating with companies to cope with the issue.
The Aomori prefectural city of Hachinohe is known for its catches of mackerel and Japanese flying squid. However, volumes have fallen to less than one-tenth of their peak levels.
This June, the city began land-based aquaculture of the popular high-end barfin flounder in collaboration with local fishing companies and financial institutions. Calling it a first-time endeavor, a city official said, “We want this to be a model project for reviving Hachinohe’s fisheries.”
Mie Prefecture plans to start experimental mackerel aquaculture, both at sea and on land from fiscal 2023, to compensate for poor wild mackerel catches.
The town of Shiranuka in eastern Hokkaido has turned to catches of yellowtail, which has seen a surge in recent years, to make up for the lack of salmon, the local specialty. The town built a new tank facility to preserve the freshness of yellowtail along with a processing plant, and is working on branding it as gokkan-buri, or yellowtail caught in extremely cold water.
Agricultural products have also been affected. Aomori Prefecture, Japan’s top apple producer, has seen poor coloring on the fruits, leading farmers to turn to growing peaches, which are relatively heat-tolerant. The area of peach cultivation has seen an increase of 1.4 times over the past decade.
The Agriculture, Forestry and Fisheries Ministry established its Climate Change Adaptation Plan in August 2015. It is advancing countermeasures across various sectors, including developing crops that are tolerant to high temperatures and transplanting high-water-temperature-tolerant culture breeds into seaweed beds, where fish can spawn and grow.