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.

Abstract
1. INTRODUCTION
2. MATERIALS AND METHODS
    2.1. Survey period and sites
    2.2. Survey methods
    2.3. Population analysis of Z. koreanus
    2.4. Gonadosomatic index (GSI) analysis
    2.5. Analysis of relative abundancebetween Z. koreanus and Z. platypus
    2.6. Statistical analysis
3. RESULTS AND DISCUSSION
    3.1. Length-weight analysis of Z. koreanus
    3.2. Length frequency distribution
    3.3. GSI analysis
    3.4. Relative abundance of Z. koreanus andZ. platypus
CRediT authorship contribution statement
Declaration of Competing Interest
ACKNOWLEDGEMENTS
REFERENCES

• Won Seok Baek(Department of Biological Sciences, Sangji University, Wonju 26339, Republic of Korea)
• Min Seop Ko(Department of Biological Sciences, Sangji University, Wonju 26339, Republic of Korea)
• Ju Hyoun Wang(Department of Biological Sciences, Sangji University, Wonju 26339, Republic of Korea) Corresponding author
• Hwang Goo Lee(Department of Biological Sciences, Sangji University, Wonju 26339, Republic of Korea) Corresponding author
• Jong Bin An(Forest Biodiversity Conservation Division, Research Official, Korean National Arboretum, Pocheon 11186, Republic of Korea)
• Yong Chan Cho(DMZ Botanic Garden, Research Official, Korean National Arboretum, Yanggu 24564, Republic of Korea)