A seafood label can promise one species while the food inside is another. In Bulgaria, a broad check of shop-bought seafood found that this was not a rare mistake, but a problem affecting about one product in nine. Seafood moves through a global, complicated supply chain, and that complexity creates more opportunities for deceptive behavior.

Misdescriptions, false labels, and species substitutions can cost consumers money and weaken confidence in the industry. The risk is not only financial. A substitution can also create a health risk if a toxic species is present or if an allergen is left off the label.

So the survey asked a simple question: does the species named on seafood sold in Bulgarian shops match what is actually in the package? Products from five broad groups were collected from shops in four cities across the country over three years. First, the species was identified from the product's biological material using molecular methods, to test whether the labeled species designation was compliant.

Next, the label was compared with Bulgaria's official list of seafood trade names to verify the use of authorized commercial designations. Finally, the labeled designation was compared with the accepted official designation to check whether Bulgaria's list matched the products available in shops.

DNA barcoding used mitochondrial and nuclear genes to identify whitefish, crustaceans, and mollusks; Mytilus products instead used a previously validated RFLP PCR protocol. The survey used DNA-based identification across fish, shellfish, and other seafood groups, with a separate validated test for products sold under a broad mussel label.

A six-hundred-fifty-five to six-hundred-fifty-eight base-pair fragment of the COI gene was chosen as the standard target for species identification across all product categories. When that elective target failed to identify the species, two mitochondrial genes, cytochrome b and sixteen S ribosomal RNA, plus one nuclear gene, PEPCK, were used to improve discrimination.

Products labeled as Mytilus were tested only with a separate DNA pattern test designed for that group. All two hundred eight PCR products intended for post-sequencing analysis returned readable sequences, providing material for the sequence-length and post-sequencing results reported in the study.

A final species allocation was reached for one hundred eighty-eight of one hundred ninety-nine products, or ninety-four point five percent; most used COI barcoding, while others used an additional target or a separate PCR-RFLP protocol. The study showed that molecular methods could assign species to most products, using COI barcoding, additional targets, or PCR-RFLP across the sample.

Then came the surprise: the label and the biological identification disagreed in 22 products, giving an overall mislabeling rate of 11 percent. The substitution incidents were recorded in a separate table. A genetic check found that fish sold under one name were sometimes entirely different species, including lower-value replacements; among the whitefish products listed here, the mismatch rate was fourteen percent.

But the problem was larger than incorrect labels. The official list of accepted seafood names did not adequately describe the range of species present on the market. In other words, the official list failed to describe the full basket of species present on the market at the time of sampling.

The proposed response is regular DNA-based monitoring aimed at choosing reliable suppliers across processing and retail. Different DNA tests can be combined when one test cannot identify a species clearly. The study also calls for the official list of commercial names to be updated and expanded, because the current list does not describe the variety of products on sale.

For shoppers, the practical goal is a seafood market that is easier to trust: the name on the package should match the food inside, and the route from supplier to shop should be more transparent. The study found that DNA checks can reveal whether seafood matches its label, but accurate identification also needs clearer official names and better tracking from suppliers to shops.