The Agriculture, Forestry and Fisheries Ministry will survey retail stores starting Wednesday to check the accuracy of tuna package labeling, ministry officials said.
The move comes in response to reports of false labeling that resulted in overpricing.
Tuna prices vary considerably according to the type and origin but are difficult to differentiate just by looking at the fish.
In the so-called emergency survey, to be conducted in accordance with the Japan Agricultural Standards Law, the ministry will carry out further investigation on suspicious cases, including looking into dealers that sold the products to retail stores and conducting DNA tests on the products, the officials said Tuesday.
If inspectors find a clear violation of the law, the ministry will release the names of the offending businesses, they said.
Japanese consume various types of tuna, including bluefin, southern bluefin and bigeye.
The average price of bluefin per kilogram is more than 1,000 yen higher than the more abundant bigeye, according to ministry statistics.
There have long been reports of false labeling as consumers tend to prefer fresh domestic products over frozen or imported ones.
Under the JAS Law, tuna caught by Japanese fishing boats are to be labeled "domestic product," while those caught by Taiwanese fishing boats are to be labeled "product of Taiwan," even if the catches are from the same area.
Similarly, tuna that had once been frozen must be labeled "defrosted" and that grown in fish farms must also be so labeled.