Molecular characterization of icefish, (Salangidae family), using direct sequencing of mitochondrial cytochrome b gene

Abstract

The Salangidae fish family includes the genera Neosalanx and Protosalanx, known as icefish or silverfish, which are imported frozen from China to Italy. The variable morphological characteristics and the small size make their particular species extremely difficult to identify. As a consequence it is not feasible to verify the precise identity of the product on the market. This means that Chinese fish can be used to fraudulently replace some much more expensive Italian species, which are similar in shape and size. Ten specimens of Neosalanx taihuensis directly collected from Lake Taihu and two hundred specimens of icefish collected from forty markets (twenty-seven from Italy and thirteen from China) were examined by direct sequencing of a portion of mitochondrial DNA belonging to the cytochrome b (cytb) gene in order to identify them at a specie level and to investigate any potential mislabelling. A BLAST analysis of the obtained sequences identified 90% of market samples as N. taihuensis, which rose to 93% when only products collected in Italy were considered. A phylogenetic tree was also constructed and the high bootstrap values obtained further supported our findings. Our results are also in agreement with some reports by Chinese authors, who describe this species as the most exploited of the Salangidae family in China in terms of internal consumption and exports. Furthermore, these findings corroborate the documentation collected from all over Italy, which reports N. taihuensis as being the only regularly imported species of icefish. The other species of salangids identified were Neosalanx anderssoni and Protosalanx chinensis. Overall, 15% of samples collected on the Italian market were mislabelled, thus confirming the existence of commercial frauds. By verifying the presence of one main icefish species on the Italian market (N. taihuensis), this study has contributed in identifying a precise target for inexpensive and rapid molecular analytical methods aimed at detecting and preventing fraud involving icefish.