Bahaba taipingensis (Chinese bahaba) is a critically endangered fish endemic to China’s coastal waters, valued for both ecological and economic reasons and known as the “panda of the sea”. Captive breeding and stock enhancement are key conservation strategies, yet the genetic composition of released individuals directly affects program outcomes. This study combined mitochondrial and whole-genome resequencing to compare F₁-generation fish with wild populations. At the mitochondrial level, 60 SNPs were detected in F₁ individuals and 72 in wild populations, with haplotype analyses revealing retention of most common maternal lineages but reduced diversity. Nuclear genome analysis showed comparable genetic diversity between groups. Nucleotide diversity (π) was 0.000423 in F₁ fish and 0.000401 in the wild population. However, the F₁ cohort exhibited a higher inbreeding coefficient (F_IS = −0.030) than the wild group (F_IS = −0.118), suggesting early allele frequency shifts, thereby suggesting early genotype frequency shifts. Runs of homozygosity (ROH) analysis showed that the total number and length of ROH regions in the F₁ cohort (686, 283,089.25 kb) were significantly greater than those in the wild population (171, 52,607.30 kb). Genome-wide F_ST between groups was 0.035, and PCA indicated genetic homogenization in F₁ fish. N_e analysis showed that the wild population declined rapidly over generations and stabilized at a low level, indicating genetic diversity loss under environmental stress and highlighting the role of artificial breeding. These findings highlight the need for improved broodstock management and long-term genetic monitoring.

The wild resources of Spinibarbus caldwelli, once an important economic fish in southern China, have been drastically reduced in recent years due to environmental changes and human activities. The Liuxi River S. caldwelli National Aquatic Germplasm Reserve was established in Conghua District, Guangzhou city, and the release of S. caldwelli was carried out. However, traditional fishery resource survey methods yield less accurate results when the abundance of the surveyed species is low or when they are difficult to catch. As a non-destructive and non-invasive approach, environmental DNA (eDNA) is widely employed in aquatic species monitoring, though its detection efficiency may be affected by environmental conditions. Therefore, this study explored the eDNA monitoring methods of S. caldwelli in Liuxi River from the following four aspects: (1) the relationship between eDNA release and biomass/abundance; (2) the concentration and diffusion range of eDNA over time in a lentic ecosystem; (3) the diffusion range of eDNA in a lotic ecosystem; and (4) the effects of eDNA application in field monitoring. Our results showed a correlation between eDNA concentration and abundance/biomass of S. caldwelli. eDNA of S. caldwelli can diffuse up to 18 m in lentic ecosystems within 2 h and decreases with distance. eDNA of S. caldwelli released by 10 individuals in Liuxi River could be detected 900 m downstream. Field studies in Liuxi River showed that the eDNA method has high sensitivity in detecting the presence or absence of species and is highly consistent with the results of traditional methods. This study explored the application of environmental DNA technology in species monitoring in Liuxi River. Our aim was to evaluate the applicability and potential of eDNA in ecological monitoring of stream fishes.

Alepes djedaba is a coastal fish species of high economic value. However, information on its early developmental biology remains incomplete, which limits its application in large-scale seed production. In this study, fertilized eggs were obtained through hormone-induced spawning. Under controlled conditions, microscopic observation and histological sectioning were used to systematically record and analyze embryonic development, larval growth characteristics, and the gonadal development potential of the artificially bred first-generation (F1) offspring. The results showed that the fertilized eggs of A. djedaba are spherical and pelagic with a single oil globule. The egg diameter is (672.02 ± 10.03) μm, and the oil globule diameter is (189.76 ± 8.82) μm. At a water temperature of 24.50–24.97 °C, embryonic development is divided into 6 periods (20 stages), taking 19 h 28 min to complete hatching with an average hatching rate of 22.9% ± 15.6%. The total length of newly hatched larvae is (1.43 ± 0.09) mm, with an average daily growth of 0.39 mm from 0 to 21 days post-hatching (DPH). Furthermore, the testes of the F1 generation cultured in captivity exhibit complete tissue structures and mature spermatozoa, while the ovaries show orderly development primarily dominated by stage II–III oocytes with some early stage IV oocytes. This confirms at the histocytological level that the artificially bred offspring possess normal gonadal development, providing strong evidence of its reproductive potential. This study clarifies the key stages of early development and the adaptability of A. djedaba in captive environments, providing critical theoretical support and basic data for subsequent large-scale seed production and larval rearing optimization.