Disclosure of genetic diversity of mackerel fish (Scomberomorus spp.) in Indonesian waters based on the mitochondrial cytochrome oxidase subunit II (COII) gene

Mackerel fish (Scomberomorus spp.) represents a significant marine fisheries commodity in Indonesia, characterized by its high commercial value and nutritional content. To understand the intraspecific interactions and genetic variability of Scomberomorus spp., a more extensive research of Scomberomorus spp. populations, including both cultivated and wild specimens, is required. This study aimed to explore the genetic diversity of mackerel fish in Indonesian waters, focusing on the mitochondrial DNA (mtDNA) cytochrome oxidase subunit II (COII) gene, which encodes the second subunit of cytochrome c oxidase (complex IV), is essential for aerobic respiration and energy transformation. Muscle tissue samples from 18 individual mackerel fish collected from various regions in Indonesia, including Palembang, Cilacap, Rembang, Banjarmasin, Ambon, and Fak-Fak Regencies, were utilized. The genomic DNA was isolated and amplified using specific primers: CO2TF (5'-ACCGCTCTGTCACTTTCTTC-3') and CO2TR (5'-ATGTCACTAAGGGTGGTTGG-3'). Subsequently, the obtained amplicons were subjected to sequencing. The sequence data were then analyzed using the MEGA11 and DnaSP 6 software. Our findings revealed 120 variable sites within the 691 base pairs of mtDNA COII sequences, resulting in a nucleotide diversity (Pi) of 0.07169. Furthermore, we identified eight haplotypes, demonstrating a haplotype diversity (Hd) of 0.8889. Remarkably, all mackerel samples from Palembang and Cilacap clustered into discrete haplotypes, specifically haplotype 1 and haplotype 2, respectively. Our phylogenetic analysis delineated three distinct clades. Clade I, closely related to Scomberomorus cavalla, encompassed all individuals from Ambon, Palembang, Rembang, and one from Banjarmasin. Clade II, associated with Scomberomorus niphonius, included individuals from Cilacap and two from Banjarmasin. Clade III, linked to Scomberomorus semifasciatus, exclusively consisted of individuals from Fak-Fak (Papua). In conclusion, Indonesian waters harbor diverse genetic variations within Scomberomorus spp., and population relationships based on the mtDNA COII gene exhibit notable complexities. Future research endeavors should focus on further elucidating the diversity and relationships among Scomberomorus spp. in diverse Indonesian populations.