DNA barcoding and metabarcoding reveal labeling accuracy and species substitution in squid and surimi from Los Angeles markets

Accurate species identification of seafood remains a persistent challenge in local and global marketplaces. This is particularly true for processed products that obscure diagnostic features. Here, we conduct a dual-molecular investigation into frozen squid and imitation crab products sold at American, Asian, and Hispanic grocery stores in Los Angeles, California, to assess label integrity under current U.S. Food & Drug Administration (FDA) guidance. Forty-eight squid samples from 13 retailers underwent DNA barcoding and yielded high percentage matches to 10 species across six genera. Despite broad labeling as ‘squid’, all samples matched FDA Acceptable Market Names with a 0 % mislabeling rate. In contrast, DNA metabarcoding of 43 imitation crab products revealed an average of six detected species per sample, with only 72 % of samples containing at least one package listed seafood ingredient. Gadus chalcogrammus (Alaska pollock) and Doryteuthis gahi (Patagonian squid) were the most frequently detected species, with the former often included as a listed ingredient and the latter never listed. 95 % of imitation crab products contained at least one undeclared species, including detection of endangered shark species and squid species prone to illegal fishing. Our results illustrate a high labeling fidelity for single species packaged squid, yet a discrepancy between legal labeling allowances and actual product composition for blended species surimi. Based on our findings, we encourage refining and the addition of routine DNA-based surveillance of blended seafood products to improve labeling credibility, consumer confidence, and supply chain integrity. • 100 % of sampled squid were accurately labeled based on current FDA guidelines. • 38 unique species were detected in imitation crab samples using DNA metabarcoding. • DNA sequencing failed to detect any listed ingredient for 28 % of imitation crab samples. • Nearly all imitation crab samples contained undeclared species including squids or sharks. • Results illustrate a discrepancy between legal label allowances & surimi product content.