Country-of-origin violations have occurred in which some merchants have fraudulently sold cheap Japanese yellowtail (Seriola quinqueradiata) by presenting them as domestic Korean products. There are many methods for determining the origins of marine organisms, such as molecular genetic methods and isotope analysis. However, this study aimed to develop a method for determining the origins of aquatic products using metabolite analysis technology. Ten yellowtail each from Korea and Japan were analyzed by capillary electrophoresis–time of flight/mass spectrometry (CETOF/MS). Hierarchical cluster analysis (HCA) and principal component analysis (PCA) results showed highly differing aspects between the Korean and Japanese samples. In the tricarboxylic acid (TCA) cycle, citric, malic, oxaloglutaric, and fumaric acids exhibited significant differences between Korean and Japanese yellowtail. Sixteen of the twenty essential amino acids analyzed as metabolites also differed significantly. All amino acids were involved in protein digestion, absorption, and metabolism. All 16 amino acid contents were higher in Japanese yellowtail than in Korean yellowtail, except for glutamine. The fasting period was found to be the biggest factor contributing to the difference in amino acid contents, in addition to environmental factors (including feeding habits). These significant differences indicated that metabolomics could be used to determine geographical origin.

Red seabream (Pagrus major), a migratory fish, is characterized by high protein levels in the muscle. South Korean and Japanese red seabreams have a general distribution pattern; however, distinguishing them based on their geographical origin is difficult. In this study, we used capillary electrophoresis time-of-flight mass spectrometry (CE-TOF/MS) to analyze the red seabream muscle metabolome to investigate how can distinguish the origin of the fish. The metabolites were extracted using 50% acetonitrile in water. Chromatographic separation was successfully used to classify the metabolite profiles of Japanese and South Korean red seabream. Principal component analysis and hierarchical cluster analysis showed good ability to categorize the samples according to their origin. Amino acids showed the greatest quantitative difference in South Korean and Japanese muscle samples. Specifically, the L-alanine, L-glutamic acid, L-isoleucine, dimethylglycine, and L-valine levels in Japanese red seabream samples were significantly higher than those in South Korean samples. In contrast, the levels of trimethylamine N-oxide and inosine monophosphate in South Korean muscle samples were significantly higher than those in Japanese red muscle samples. The monitored metabolite profiles suggest that South Korean and Japanese red seabreams can be identified on the basis of amino acid levels.

Red seabream (Pagrus major) is widely consumed in East Asia. As nuclear wastewater is discharged into Japanese waterbodies, the country of origin of marine products must be accurately labeled. Here, we aimed to discover candidate metabolite biomarkers to discriminate between Korean and Japanese red seabream using LC-Orbitrap mass spectrometry. In total, 95 and 138 putative metabolites were detected via chromatographic separation of fish sampled in the warm and cold seasons, respectively. The spectrometric and chromatographic data were analyzed using principal component analysis and orthogonal partial least squares discriminant analysis. We identified 12 and 19 influential metabolites to discriminate between each origin fish in the warm and cold seasons, respectively, using variable importance in projection scores and p values. Anserine was further selected as a candidate biomarker based on receiver operating characteristic curve analysis. This study provides a basis for using anserine to determine the geographic origin of red seabream.

The species Niphon spinosus (Cuvier, 1829) is the only representative of the family Niphonidae and the genus Niphon, and its taxonomic history is complicated; it is still unclear in a phylogenetic sense. In this study, we report the complete mitochondrial genome of N. spinosus (OP391482), which was determined to be 16,503 bp long with biased A + T contents (53.8%) using next-generation technology. The typical set of 13 protein-coding genes (PCGs), 2 rRNA genes, 22 tRNA genes, and one control region (D-loop) are included in the mitochondrial genome. The H-strand encoded 28 genes (14 tRNA, 2 rRNA, and 12 PCGs), and D-loop, whereas the L-strand encoded the remaining 9 genes (8 tRNA and ND6). Its nucleotide composition, gene arrangement, codon usage patterns, and tRNA secondary structures are identical with other members of the Percoidei suborder. Furthermore, we reconstructed phylogenetic trees based on the 13 PCGs. The resulting phylogenetic trees showed N. spinosus placing as a separate lineage within the family Niphonidae, its close relationship to Trachinus draco (Trachinidae), and the clustering of major subfamilies like Luciopercinae and Percinae of the Percoidei suborder. These findings will contribute to future studies on the evolutionary history, population genetics, molecular taxonomy, and phylogeny of N. spinosus and related species.

Scorpaena neglecta (Temminck and Schlegel, 1843) is a marine fish, in the family Scorpaenidae, order Scorpaeniformes, class Actinopterygii of the phylum Chordata. The first species of Scorpaena with a complete mitochondrial genome is described in the present study. The circular mitochondrial genome of S. neglecta has 17,202 bp with 54.75% A + T content and encodes 37 genes, including 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA), and two ribosomal RNA (rRNA). The phylogenetic tree indicates S. neglecta clustered into one branch and is closely related to other Scorpaenidae species. The mitochondrial genome structure and gene content of S. neglecta will support the study of evolution and phylogenetic relationships among Scorpaenidae species.