A seafood label can look perfectly ordinary while naming the wrong species. In Bulgaria, DNA testing found that eleven percent of the sampled products were mislabeled, exposing both consumer risks and weaknesses in traceability.

Globalization and the complexity of the supply chain, together with the distribution system, can expose the seafood market to an increased opportunity for deceptive behaviors. Those incidents include misdescriptions, mislabeling and economically motivated species substitutions, causing economic damage and loss of confidence in the sector chain.

Substitution can also create health risks when toxic species are present or allergens are omitted. EU food law treats safety, transparency, and fair trading as founding principles, and Regulation Number 1379 slash 2013 sets specific rules for seafood labeling and presentation.

Member States must publish and update official seafood trade names linked to the scientific names accepted for sale nationally. In Bulgaria, official controls in this area are delegated to the Bulgaria Food Safety Agency. Fraudulent incidents remain well documented, but labeling compliance and mislabeling rates are rarely reported for Central-Eastern and Eastern European countries.

The regulation promotes identity checks using available technology, including DNA testing, to deter fraudulent substitution practices. A 2017 pilot study on the Bulgarian market found an overall substitution rate of seventeen point seven percent. The study also highlighted the urgency of revising Bulgaria’s official list of seafood trade names.

The new survey expanded beyond the pilot study: it covered three years, five taxonomic classes, retail settings in four cities, and molecular identification using DNA barcoding and PCR–RFLP. The labeled designations were checked against the official list, and the list was compared with the products available at retail.

Each product was classified as unprocessed or processed according to Regulation Number 852 slash 2004, then assigned a numerical code with its labeling information recorded. Finally, one to five grams of muscle tissue were collected, dehydrated in ninety-five percent ethanol, and sent for molecular identification.

A six-hundred-fifty-five to six-hundred-fifty-eight base-pair fragment of the COI gene was selected as the main target for species identification across product categories. Additional mitochondrial and nuclear genes were used when COI alone could not identify the species.

Products labeled Mytilus sp. were tested only with PCR–RFLP targeting the nuclear PAP gene. The sequences were compared with reference sequences in GenBank and, for COI, the BOLD database. For COI and cytb, species allocation required an identity score above ninety-eight percent; for sixteen S ribosomal RNA and PEPCK, the threshold was one hundred percent.

Table one summarizes the molecular targets, primer pairs, taxonomic classes, and amplification conditions used by the authors. The elective COI target spans six hundred fifty-five to six hundred fifty-eight base pairs, while additional targets include cytb at one thousand one hundred fifty base pairs, 16S rRNA at approximately five hundred fifty base pairs, and PEPCK at five hundred ninety-five base pairs.

It also documents a PAP RFLP protocol for Mytilus species, including Aci-I digestion, making the study’s laboratory workflow explicit and reproducible. The label information was checked against the mandatory requirements of Regulation Number 1379 slash 2013, including the commercial and scientific names, production method, area, fishing method, and thawing information.

The molecular results were directly compared with the labeled scientific names, and products were non-compliant when the species did not match. Most samples were unprocessed: seventy-six point four percent, or one hundred fifty-two samples, compared with twenty-three point six percent, or forty-seven samples, that were processed.

Figure one counts the labeled seafood products collected at retail outlets, grouped by taxonomic class: fish, crustaceans, cephalopods, bivalve mollusks, and gastropods. The chart shows one hundred fish products, thirty-eight crustacean products, forty cephalopods, sixteen bivalves, and five gastropods, with the most commonly encountered species in each class highlighted in green.

This matters because the authors identify a fairly limited variety of species in large retail outlets, alongside the broader evidence that the market is strongly oriented toward imported, prepared, and processed seafood. DNA was successfully extracted from all one hundred ninety-nine products.

All one hundred ninety-nine DNA samples were amplified, producing two hundred eight PCR products for sequencing and thirteen PCR products from Mytilus sp. products for RFLP analysis. All two hundred eight PCR products intended for post-sequencing analysis produced readable sequences.

A species-level identification was reached for one hundred eighty-eight of the one hundred ninety-nine products, or ninety-four point five percent. Figure three shows the PCR–RFLP results for thirteen MB Mytilus products after Aci–I digestion of the PAP target.

The gel bands display fragment patterns of either one hundred twenty-three base pairs or, for some samples, seventy-seven and forty-four base pairs, with the ladder providing size references. The accompanying table compares these RFLP patterns with molecular identification, supporting species-level allocation for the MB products where sequencing alone was insufficient.

For the remaining eleven products, the analysis reached only genus-level allocation: eight fish products were assigned to Alepocephalus sp., and three crustacean products to Metapenaeus sp. or Heterocarpus sp. Even so, all the data were sufficient for checking labeling compliance.

The main limitations were low barcode resolution, unreliable reference sequences, or missing reference sequences. The molecular results identified twenty-two substitutions among one hundred ninety-nine products, corresponding to an overall mislabeling rate of eleven percent.

Table two lists individual mislabeled products by taxonomic class, showing the declared species alongside the species identified through molecular testing. For whitefish, the table reports one hundred products and a substitution rate of fourteen percent, with examples including Gadus morhua identified as Pollachius virens and Theragra chalcogramma identified as Merluccius productus or Merluccius hubbsi.

The authors also provide FAO distribution areas, making the geographic mismatch part of the evidence for each substitution. The overall mislabeling rate was lower than the pilot study’s rate of around seventeen percent. Whitefish had the highest mislabeling percentage at fourteen percent, followed by bivalve mollusks at twelve point five percent and cephalopods at ten percent.

The results suggest that substitutions within whitefish may occur both at fishing or first sale and later during processing or packaging. Geographically distant substitutes may indicate substitution later in the chain, and could also conceal an attempt to reallocate products linked to illegal fishing.

Table three compares scientific names found on product labels with two official designation lists: Ordinance Number four of thirteen January two thousand six, and Ordinance Number thirteen of thirty November two thousand twenty-one. The many “no” entries show that the list in force during sampling did not adequately describe the species represented on the market, while the updated list also changes individual entries, such as Merlangius merlangus euxinus and Mytilus galloprovincialis remaining accepted, and Rapana venosa becoming accepted.

The authors link these discrepancies to possible substitution and outdated taxonomy. The comparison clearly highlighted that the official list in force during sampling was ineffective at describing the basket of species present on the market.

The eleven-percent mislabeling rate and the substitution incidents highlighted the need for DNA-based monitoring systems oriented toward supplier selection among food business operators in processing and retail. An integrated approach combining different DNA analytical methods may support univocal seafood identification.

The official commercial-designation list requires further updating and expansion, and the survey data could support a government monitoring plan developed with wholesalers and sellers. The survey shows that DNA-based monitoring, combined with an updated official trade-name list, is needed to reduce substitutions, protect consumers, and make Bulgaria’s seafood market more transparent.