Roasted fish fillet is a popular snack food in the People's Republic of China, and the market appeal can be reflected by the high price, which exceeds 330 RMB/kg in some cases. However, the labeled fish common name generally cannot be connected with a particular species, and the processing treatments make it a challenging task to identify fish species based on morphological characteristics. This study used full DNA barcoding and mini-DNA barcoding for species identification of 202 specimens sorted from 64 roasted fish fillet products sold across China, which belonged to 32 distinct brands and claimed 16 fish common names on the label. Given the absence of a harmonization in defining these common names in China, scientific literature and the Latin-Chinese dictionary of fish names (http://fishdb.sinica.edu.tw/) were consulted to define at least the family for each common name, and an identified species outside the expected family was determined to be mislabeled. Results highlighted a high mislabeling rate of 75.5%. Even worse, fish species were identified as belonging to multiple families, not only from several products of the same brand under the same common name but also from several specimens sorted from the same product. Moreover, a health issue was highlighted by the identification of toxic Tetraodontidae species from one product. To protect the consumers from economic loss and even health risks, we recommended amendments to existing legislation and the compilation of a list of acceptable market names for fish species in China. Meanwhile, DNA barcoding is a powerful tool in fish forensics, and we recommended the use of this technique to assure the accurate species labeling of fish products. HIGHLIGHTS

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Summary Using species outside the order Gadiformes to prepare codfish products has been widely revealed as a new type of fraud in China, highlighting the necessity to establish proper methods for codfish species identification. This work aimed to develop a new SYBR Green real‐time PCR assay for the detection of codfish ingredient (mainly the eight Gadiformes species, Gadus morhua, Gadus macrocephalus, Theragra chalcogramma, Pollachius virens, Melanogrammus aeglefinus, Merluccius merluccius, Merluccius australis and Albatrossia pectoralis) in processed fish products based on mitochondrial 12S rRNA gene. Results highlighted the positive Cq (cycle quantification value, average value 19.18 ± 1.49) only from the eight Gadiformes species, with no fluorescent signal (Cq > 32) for the other sixty‐seven non‐Gadiformes species. The absolute limit of detection was 0.048 ng genomic DNA. Methodology validation succeeded in twenty‐six commercial products. These results demonstrated that the newly developed method is suitable for the identification of codfish ingredient in processed fish products.

With the expansion of e-commerce, an increasing number of Chinese consumers are turning to online markets to purchase foreign seafood. When buying seafood online, customers cannot physically evaluate the product, and the market Web page instead of the seafood label conveys all of the product information. However, specific regulations concerning the information presented on the Web page have not been created, which may foster seafood fraud and misdescription. Because mislabeling of seafood has become a widely reported issue in the Chinese offline market, the online scenario must be investigated comprehensively. This study focused on various seafood products that originated from 20 countries and were sold by one of the largest e-commerce companies in China. For each country, only the product with the greatest overall monthly transaction volume was selected, and 5 samples were purchased per product for a total of 100 samples. The Web page description (including the heading of the Web page and the description of the commodity) and the label of the received products were compared to evaluate the description consistency. DNA barcoding technology was used for seafood species identification, and the scientific names retrieved from the sequence analysis after consulting the Barcode of Life Data systems and GenBank were compared with the expected species, genus, and family to determine the description authenticity. Only 25% of the samples had consistent descriptions on the Web page and on the label of the received product. Most of the inconsistency originated from the geographical origin, and only four products (G10, G50, G19, and G69) had inconsistent species, genus, and family descriptions. Molecular analysis revealed that in 65% of samples the species was correctly described. The online seafood market presents challenges regarding seafood fraud and opportunities for seafood species substitution. HIGHLIGHTS