The construction of a reservoir dam alters the environment within its basin, including composition of the fish community, fish biodiversity, and the river ecosystem itself. This study was conducted in the Sanbanxi Reservoir and used eDNA metabarcoding technology comprising eDNA capture and extraction, PCR amplification, sequencing and database comparison analysis, and other environmental DNA metabarcoding standardized analysis processes to characterize the composition and diversity of fish communities and assess their current status. A total of 48 species of fish were detected. Previously, 68 species of fish were screened and identified in this reservoir based on the reports of Dai and Gu. The results for fish community composition showed that species of the order Cypriniformes are still the most dominant in the Reservoir with 38 species of cyprinids, accounting for 90.81% of all OTUs. Carp were no longer the dominant species, and Spinibarbus denticulatus, Homalopteridae, Cobitidae, and Sisoridae were not detected, with the exception of Misgurnus anguillicaudatus (Cobitidae). These families have the common characteristic of being adapted to survive in fast-water, sandstone substrate habitats. The results also show that two of the sampling sites, sbx03 and sbx10, significantly differed from other sampling sites due to their geographical environment. The impact of the construction of reservoirs on freshwater fish communities is extreme, since the transformation from a lotic to a lentic habitat contributes to habitat destruction and constrains fish in movement. The change in the aquatic environment before and after the storage of water in the Sanbanxi Reservoir has reduced the number of fish species found in the reservoir, and species characteristically found in fast moving, rapids habitats are virtually absent. The profound change in the aquatic environment from that of a lotic to a lentic habitat leads to changes in the composition of fish populations in the reservoir and to a certain extent a reduction in the ecological stability and species diversity within the reservoir. Therefore, the protection of fish diversity in the reservoir is of great significance to the stability of the ecosystem.

Paraqianlabeo lineatus is a small-sized fish which is endemic to Guizhou province, China. The complete mitochondrial genome of P. lineatus is 16,598 bp in total length, with 37 genes, including 13 PCGs, 22 tRNA genes, two rRNA genes (16S and 12S) and a non-coding region (D-loop). The positions and sequences of genes were consistent with congeners of Labeoninae. The nucleotide composition of the mitogenome was A (31.5%), T (26.7%), G (15.9%), C (25.8%) and was slightly A + T biased. Phylogenetic analysis conducted using Bayesian Inference method showed that P. lineatus clustered with Pseudogyrincheilus procheilus within the subfamily Labeoninae. The results may provide helpful data for further studies of the evolutionary history of Labeoninae.

An accurate assessment of fish stocks is crucial for maintaining the health and stability of aquatic ecosystems. To understand the characteristics of fish diversity in the Qingshui River, this study utilized high-throughput sequencing data obtained through environmental DNA macrobarcoding technology (eDNA). The research explored differences in fish diversity and community characteristics in the Qingshui River by analyzing fish community structure, α diversity, β diversity, and the redundancy of environmental factors. This analysis aims to provide data support for water ecological monitoring and management. The results were as follows: (1) A total of 91 species of fishes from 18 families and seven orders were detected in the eDNA survey, and the dominant species was Cypriniformes, accounting for 72.5%. (2) There were significant differences in α diversity analysis in the Qingshui River (p < 0.05). (3) The fish community structure was similar in β diversity analysis. (4) In the redundancy analysis of environmental factors, pH, DO, TN, TP, ${\mathrm{N}\mathrm{O}}_2^{-}$ and ${\mathrm{M}\mathrm{n}\mathrm{O}}_4^{-}$ have the greatest impact on the Qingshui River Basin. eDNA technology has the advantages of high efficiency and low harm and can be used for water ecological monitoring and management. It provides a scientific basis for fish protection and a valuable reference for fish monitoring in the future.

The microphthalmia-associated transcription factor (Mitf) family is central to melanocyte biology. Teleosts possess two mitf paralogs, mitfa and mitfb, yet their functional divergence remains incompletely understood. Here, we characterized the coding sequences, phylogeny, tissue distribution, developmental expression, cellular localization, and stress responsiveness of mitfa and mitfb in Congjiang natural mutant crucian carp (NMCC). Both genes encoded proteins containing the characteristic bHLH-ZIP domain. Phylogenetic analysis revealed that teleost mitfb clustered with the tetrapod mitf clade, indicating closer evolutionary affinity than mitfa. mitfa was predominantly expressed in skin and eyes, whereas mitfb showed broad tissue distribution. Both paralogs were constitutively expressed in skin across developmental stages; mitfa levels remained consistently lower than mitfb. Both transcripts were localized to melanocyte-containing regions of the skin. Transcriptomic analysis following high temperature (34 °C), UV radiation, and combined stress (48 h) revealed that mitfa was significantly upregulated by thermal stress, while mitfb showed no significant changes. Profiling of DNA damage response pathways uncovered extensive, stress-specific transcriptional remodeling. High temperature broadly suppressed apoptotic genes while upregulating tsc2, gadd45b, and cdip1; UV triggered widespread apoptotic gene activation. Combined stress elicited a hybrid signature. Notably, robust DNA Damage Response pathway remodeling contrasted with muted mitf responses, suggesting that DNA Damage Response-to-pigmentation signaling may operate predominantly at post-transcriptional levels. These findings reveal a substantial regulatory divergence between mitfa and mitfb, with mitfa maintaining a conserved melanogenic role while mitfb has been co-opted for broader functions in non-pigmentary tissues. The differential stress responses of the two paralogs further provide new insights into tissue-specific genotoxic stress signaling and melanogenic regulation in teleosts.

Pareuchiloglanis feae is mainly distributed in Irrawaddy (China and Myanmar), Salween (China and Myanmar), and the Yangtze River drainage areas. In this study, the complete mitochondrial genome of P. feae, which has a circular structure of 16,863 bp, including 13 protein-coding genes, 2 ribosomal RNA (rRNA), 22 transfer RNA (tRNA) genes, and a non-coding control region (D-loop), is being reported for the first time. The A, T, C, and G content were 31.36, 15.69, 28.04, and 24.91%, respectively. Bayesian inference and maximum likelihood method showed that P. feae clustered with P. anteanalis and P. sichuanensis. Our results provide further information and references for clarifying the phylogenetic relationships within Glyptosternoid fishes.

Eonemachilus caohaiensis is a bony fish endemic to Guizhou Province, China. In this study, we report its complete mitochondrial genome for the first time. The circular mitochondrial genome is 16,570 bp in length and consists of 13 protein-coding genes (PCGs), two rRNAs, 22 tRNAs, and a non-coding control region (D-loop). The overall nucleotide composition is A: 30.84%,T: 27.02%,C: 26.00%, and G: 16.14%. Maximum likelihood phylogeny positioned E. caohaiensis as a sister taxon to Yunnanilus niger and E. longidorsali, supporting their classification within the genus Eonemachilus. These findings provide new insights into the phylogenetic relationships within the Nemacheilidae family.