Lake Shinji Yamato Shijimi Clams (Shimane): season, origin and where to buy

Seasonal calendar

They are harvested year-round, but are at their best around July before spawning and from January to March, when they are plump.

Timing shifts with the weather and conditions in each region.

Official registration details (MAFF)

The registered description as published by the Ministry of Agriculture, Forestry and Fisheries.

Characteristics

Lake Shinji Brackish Water Clams are large and meaty, rich in minerals and amino acids, and are highly regarded by consumers as a delicious, natural health food. They are an essential ingredient in the local dishes Shijimi-jiru (brackish water clam miso soup) and Sumashi-jiru (clear soup), staple menu items both at home and in restaurants, embodying the flavors of Shimane Prefecture.

Link with the production area

Lake Shinji is a brackish lake with a salt concentration of about one-tenth that of seawater. It possesses natural conditions suitable for Yamato Shijimi (Japanese basket clams), as numerous nutrients flow in from surrounding rivers, leading to an abundant growth of the phytoplankton they feed on. During the Edo period, they were designated as the official brackish water clams for the Matsue Domain, and have long been cherished as a commoner’s delicacy. In 1981, brackish water clam harvest from Lake Shinji became the largest in Japan. As of 2024, Matsue City has ranked first in Japan for 14 consecutive years in terms of brackish water clam purchases per household.

Characteristics and link with the area: Ministry of Agriculture, Forestry and Fisheries website (https://www.maff.go.jp/e/policies/intel/gi_act/register/260319.html)

Where to buy

As a rule, only products that meet the registered standard may use a GI name (with exceptions such as prior use). Check for the GI mark and the place of origin to tell it apart from ordinary products with similar names.

Find on furusato nozei (opens in a new tab)Find online (opens in a new tab)

These links go to Japanese-language shops; check whether they ship overseas.

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FAQ

Yamato shijimi (Japanese basket clams) harvested from Lake Shinji in Shimane, also known as Shinjiko shijimi. Raised in a brackish lake about one-tenth as salty as seawater, the clams are large, meaty, and rich in minerals and amino acids. They are essential to local dishes such as shijimi soup and represent the flavors of Shimane.

Lake Shinji Yamato Shijimi Clams is produced in Matsue City and Izumo City, Shimane Prefecture.

Lake Shinji Yamato Shijimi Clams is in season (harvested or shipped) in Jan–Mar, Jul. They are harvested year-round, but are at their best around July before spawning and from January to March, when they are plump.

Look for it via furusato nozei (hometown tax donation) and online shops. Check the GI mark and the place of origin before you buy.

Lake Shinji Yamato Shijimi Clams was registered as a Geographical Indication on November 17, 2025 (Registration No. 171). The registered producer group is Lake Shinji Fisheries Cooperative Association.