Genetic Diversity and Population Structure of Blackfin Flounder (Glyptocephalus stelleri) in Korean and Japanese Waters Based on Mitochondrial DNA Control Region Sequences

The blackfin flounder (Glyptocephalus stelleri) is an important demersal fish species widely distributed in the Northwest Pacific and represents a valuable fisheries resource in Korea and Japan. Understanding the genetic diversity and population connectivity of exploited marine species is essential for effective fisheries management and conservation. In this study, mitochondrial DNA control region sequences (401 bp) were analyzed from 62 individuals collected from Jumunjin, Korea, and Maizuru, Japan, to assess genetic diversity, demographic history, and population structure. Sequence analysis identified 48 haplotypes, revealing exceptionally high haplotype diversity (h = 0.982 ± 0.010) and relatively low nucleotide diversity (π = 0.011 ± 0.006). Neutrality tests and mismatch distribution analyses indicated a historical demographic expansion during the Pleistocene. No significant genetic differentiation was detected between the two sampling locations (FST = −0.004, p > 0.05), suggesting strong genetic connectivity between Korean and Japanese samples based on mitochondrial DNA data. These findings provide important baseline genetic information for understanding population connectivity and may contribute to the coordinated management of blackfin flounder fisheries in the Northwest Pacific.