This study assessed the genetic outcomes of reintroducing Zacco koreanus into the Bongseonsa Stream by comparing the genetic diversity and population structure of the reintroduced population to those of the original populations from the Jojong and Sudong Streams. The reintroduced population in Bongseonsa Stream retained multiple haplotypes and displayed a mixed genetic composition with the original populations, indicating the reintroduction strategy’s effectiveness. The pairwise genetic differentiation value (FST) suggested that the Jojong Stream population, which is geographically closer and ecologically similar, contributed more to gene flow and potential local adaptation in the reintroduced population. Results from STRUCTURE analysis (K=2) and principal coordinate analysis (PCoA) showed no clear genetic separation among populations, supporting effective genetic integration. However, the relatively small effective population size (Ne) of the reintroduced population raises conserns about potential longterm risks of inbreeding and genetic drift, which could lead to a loss of genetic variation. Overall, the reintroduction successfully established a genetically diverse population in the short term, but continuous monitoring and adaptive management are crucial for maintaining genetic health and ensuring long-term population stability. This study underscores the importance of integrating genetic considerations into freshwater fish restoration programs and provides a reference for developing sustainable population management strategies.

This study aimed to evaluate the habitat stability and biological characteristics of the reintroduced population of Zacco koreanus in the Bongseonsa Stream, comparing it with original populations from the Jojong and Sudong Streams to assess the effectiveness of the restoration. To confirm the stable establishment of the reintroduced population, we analyzed the length-weight relationship, condition factor, length frequency distribution, gonadosomatic index (GSI), and population ratio relative to the competing species, Zacco platypus. We referenced data from previous studies conducted in 2007, 2011, 2015, and 2016, and performed field surveys in 2021 and 2025. The length-weight analysis revealed that the regression coefficient (b value) for the Bongseonsa population consistently exceeded 3.0 in 2015, 2021, and 2025, while the condition factor (K) demonstrated a positive slope. These findings indicate rapid weight gain relative to length growth, suggesting adequate food availability and effective habitat management. Over time, the length-frequency distribution gradually stabilized, and by 2025, the population exhibited a pattern similar to that of natural populations, indicating a stabilization of the life-history structure. Analysis of the GSI showed that the reintroduced population had a higher reproductive capacity than the original population. Following reintroduction, the relative abundance of Z. koreanus consistently increased, while that of the competing species Z. platypus declined. Overall, these findings demonstrate successful establishment of the reintroduced population of Z. koreanus in the Bongseonsa Stream, evidenced by stable growth, high reproductive capacity, and ecological competitiveness. The success of the restoration is attributed to habitat improvements, including enhanced water quality and stream restoration, as well as the introduction of individuals from two distinct source populations. Therefore, the results of this study are expected to provide valuable data for assessing the effectiveness of future fish restoration projects and for developing long-term habitat management strategies.

The present study is to understand the Bongseonsa stream in the National Arboretum fish fauna variation through comparison with historical data and to evaluate the stream health situated. We performed investigations over three times from April to September 2015. In the survey, 2,960 individuals which belonging to 22 species, 8 families were collected. Dominant species by number was Zacco platypus and subdominant species was Zacco koreanus. Seven Korean endemic species (Squalidus gracilis majimae, Microphysogobio yaluensis, Zacco koreanus, Koreocobitis rotundicausata, etc) were observed and showed a ratio of 36.4%. The community analysis revealed that the structure of fish community in the study sampling sites was instability in having dominance 0.79 (±0.15), diverse 1.21 (±0.60), evenness 0.58 (±0.15) and species richness 1.49 (±0.83). The values in the Qualitative Habitat Evaluation Index (QHEI) was averagely 122.9 (±44.8) in the Bongseonsa stream and this was showed to have favorable habitat surroundings. As a result of tolerance guild analysis, the total number of sensitive species and intermediate species were higher than tolerant species. Analysis was divided into A and B two groups of fiducial 12.25% in Cluster analysis degree of similarity between study sampling sites. Fish Assessment Index (FAI) was rated A and B grade in Bongseonsa stream that stream health showed favorable. However Wangsuk stream as a urban stream rated C grade and analysed the lowest grade in the whole study sampling sites. There was high correlation beteween FAI and various indexes, dominance, diverse, evenness and sensitive species and intermediate species.