Authentication of fish species served in conveyor-belt sushi restaurants in Taiwan using DNA barcoding

Fish fraud is a problem worldwide. Not only does it erode customer confidence, but it also jeopardizes public health. Typically, it is difficult to authenticate fish species identity based on morphological characters after food processing. Fortunately, DNA is relatively resistant to processing methods, and DNA barcoding has proven useful for species identification. Although fishery product mislabeling is recognized as an issue in Taiwan, a respective study on sushi has not yet been conducted. Here, we successfully DNA-barcoded 121 out of 122 sushi samples from eleven chain restaurants of the conveyor-belt type in Taiwan, revealing an overall mislabeling rate of-17.36%. We found that capelin roe is commonly used to replace other fish roe, such as herring. Tuna, which is susceptible to fraud, was always correctly labeled. We also noted inconsistent usage of Chinese common names, conflict between Chinese and English names, and ambiguous usage of Japanese kanji in Chinese labels, all serving to confuse species identity. Moreover, spurious reference sequences in the BOLD database and the lack of a standard list of common names of fishes with their corresponding scientific name both impede investigations of fish substitution. We advocate that the responsible authorities establish a reliable barcoding database for molecular authentication of fishes, publish a respective standard for common and scientific names, and legislate for more comprehensive labeling regulations based on experience in other jurisdictions to facilitate mislabeling investigations and to deter food fraud.

Automated summary

Fish fraud is a global issue, with a mislabeling rate of 17.36% found in sushi samples in Taiwan. Establishing a reliable DNA database is crucial to tackle fish substitution.