This paper describes a new Asian hard clam, Meretrix taiwanica sp. n., found in the Tamsui River estuary in northern Taiwan. This species was formerly identified as M. lusoria, and was considered to be a descendant of a clam that originated in Japan. A molecular phylogenetic analysis, however, demonstrated that Meretrix taiwanica sp. n. is closely related to M. petechialis and M. lusoria. Meretrix taiwanica is distinguished by its smaller socket width and shorter posterior dorsal margin. This species is distributed throughout the coast of Taiwan on the southern coast of China.

Saccostrea are common oysters of Indo-Pacific rocky shores. However, the taxonomy of this genus is confused. In this study, we report the complete sequence of the mitochondrial genome of S. kegaki. The complete S. kegaki mitogenome is 16,260 bp in size. The 16S rRNA gene is split into two parts by a large fragment of genes. Neighbour-joining molecular phylogenetic analysis appears to support the current taxonomic framework of Ostreidae. We expect that the complete mitogenome of S. kegaki will provide a useful resource for studies on the molecular phylogeny and conservation genetics of Bivalvia.

Understanding genetic diversity and population structure is essential for effective fisheries management. This study examined the population genetic structure, diversity, and demography of the red big eye Priacanthus macracanthus, a commercially crucial species in the western Pacific and eastern Indian Oceans, by using mitochondrial DNA cytochrome b (cytb) gene sequences (1,141 bp). A total of 206 samples were collected from 9 locations, and 101 haplotypes were obtained. Analysis revealed that (1) all haplotypes clustered into two sympatric haplogroups; (2) although the genetic distance between these haplogroups was small, nucleotide substitution patterns indicated distinct evolutionary histories; (3) migration and haplogroup distribution patterns suggested that the two haplogroups may have originated from different sources, eastern Indian Ocean and the western Pacific Ocean; and (4) recent population declines and low nucleotide diversity indicated a need for targeted management strategies. These findings provide valuable insights that can guide fisheries management and future research on the conservation of P. macracanthus populations.

The complete mitogenome of the palemargin grouper, Epinephelus bontoides, was presented in this study. This mitochondrial genome consists of 16 903 bp, follow the typical gene arrangement with 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and a non-coding control region (CR). The overall base composition was A, 28.7%; G, 16.1%; C, 28.0%; and T, 27.2%. The control region was 1200 bp in length, which located between tRNA^Pro and tRNA^Phe, rich in A + T (69.2%) content. Based on the Neighbor-Joining (NJ) tree, E. bontoides was grouped with E. trimaculatus, E. quoyanus, E. areolatus, and E. bleekeri, and then combined with E. merra formed a clade. This complete mitogenome of E. bontoides can provide essential phylogenetic information of Epinephelus.

To understand the spatial and seasonal variations of fish communities in Taiwanese estuaries, this study collected environmental DNA (eDNA) water samples and assessed environmental parameters from four estuaries in northeastern, southeastern, northwestern, and southwestern Taiwan between February and December 2023. The 12S rRNA genetic marker was used as a mini-barcode to detect fish compositions in 16 samples. Assessment of environmental parameters revealed that (1) there were significant differences between estuaries but no differences between seasons; (2) the northwestern estuary exhibited the greatest seasonal variation; and (3) the greatest spatial variation was exhibited in summer. Fish community analysis revealed that (1) fish diversity was highest in the northeastern estuary and lowest in the southeastern estuary; (2) fish compositions significantly differed among the estuaries; (3) fish compositions in the southeastern estuary exhibited the greatest seasonal variation, and those in the northeastern estuary exhibited the smallest seasonal variation; (4) fish compositions in winter slightly differed from those in the other seasons; and (5) invasive fish species were present in all estuaries. In summary, the fish compositions in Taiwanese estuaries were influenced by local environmental variables and ocean currents.