Japan In Focus

Saga: Clams released in Ariake Sea to protect nori crops

The Yomiuri Shimbun

11:02 JST, November 20, 2022

SAGA — Red tide outbreaks have been plaguing nori farmers in the Ariake Sea in recent years, and efforts are being made to roll back the hazardous wave.

The Ariake Sea, an inland body of water surrounded by four northern Kyushu prefectures, is home to Japan’s largest cultivation of nori, but red tides are damaging crops especially in Saga Prefecture.

In an effort to counter the phenomenon, the prefectural government released young shellfish that prey on phytoplankton. Red tides are a phenomenon in which phytoplankton proliferate in such large numbers that they change the color of the ocean, and the proliferation deprives nori of the nutrients needed for growth.

Courtesy of Ariake Sea fishery cooperative
Normal nori can be seen on the left, compared to nori whose color has faded.

According to the Saga prefectural government and others, the color of nori faded, turning yellowish instead of black, in the prefecture. As a result, the worst-hit area saw the value of its nori drop to less than 10% of the previous year’s level.

Employees of the prefecture’s fisheries research facility released about 1 million young ark clams measuring 1 centimeter each on Oct. 25. If the clams grow well, they are expected to be able to spawn in one to two years.

By releasing young clams, the prefectural government also aims to restore this type of clam stocks because it is a popular food ingredient. Catches of the clams have declined to less than 1% of the level seen 30 years ago.