Genetic Diversity and Population Structure of Brown Croaker (Miichthys miiuy) in Korea and China Inferred from mtDNA Control Region.

Brown croaker (Miichthys miiuy), a species of fish with significant commercial value, is found in the coastal seas of Korea, China, and Japan. The genetic diversity and population structure of a representative sample of brown croaker specimens were assessed based on the control region of their mitochondrial DNA (mtDNA). Samples from a total of 115 individuals were collected from three separate locations, one in China (Lianyungang) and two in Korea (Mokpo and Gyeongnyeolbiyeoldo Island). Analysis of the 436-base-pair mtDNA control region revealed that the haplotype diversity ranged from 0.973 ± 0.025 to 0.988 ± 0.008, while the nucleotide diversity ranged from 0.012 ± 0.006 to 0.017 ± 0.009. The level of genetic diversity, star-shaped haplotype network, significant Fu's Fs test, and analysis of the mismatch distribution all suggested that this species has experienced population expansion. Fixation index analysis indicated that the population collected at the site in China differed significantly from the two populations obtained in Korea. The findings of this study extend the general understanding of the population structure of M. miiuy and can be used to develop strategies for effective resource management.

Genetic Diversity and Variation in Mitochondrial COI Gene in Wild and Hatchery Populations of Saxidomus purpuratus.

To investigate the genetic diversity and genetic variations of four wild (Geoje, Jinhae, Yeosu, and Boryeong) and two hatchery (Goheung and Geoje) populations of purplish Washington clam (Saxidomus purpuratus), 421 bp sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene were analyzed. A total of 149 haplotypes were identified from 358 individuals from the four wild and two hatchery populations with 109 substitutions. The genetic diversity of the wild populations and Geoje hatchery population were high, whereas the total number of haplotypes, population-specific haplotypes, and haplotype diversity were comparatively low in the Goheung hatchery population. The fixation index (FST) indicated that there was no significant genetic difference between the four wild populations. However, the Goheung hatchery population was significantly different from that of the Geoje hatchery, exhibiting the most pronounced difference, and two wild populations (Jinhae and Yeosu). The low genetic diversity indices exhibited by the Goheung hatchery population might have resulted from farm propagation using a limited parental stock. Therefore, to maintain genetic diversity, a proper breeding management program using more progenitors is required in hatcheries, in addition to regular monitoring of both hatchery and wild populations.