Investigation on the Distribution of in Yuanshui Unique Fish Species National Aquatic Germplasm Resources Reserve Using Environmental DNA Technology.

Freshwater ecosystems face unprecedented challenges as the cumulative impact of human activities intensifies. While protected areas and species-specific conservation policies are widely implemented, their effectiveness remains difficult to gauge using traditional catch-based surveys. This research employed environmental DNA (eDNA) technology to assess the distribution of the endangered fish, , within the Yuanshui Unique Fish Species National Aquatic Germplasm Resources Reserve (YUFRR) in Hunan, China. Over a 2-year period, we conducted comprehensive eDNA survey multiple sites within the YUFRR, confirming the species' continued existence in the area. In September 2022, eDNA was detected at 8 of 60 sampling locations, while a follow-up survey in May 2023 identified its presence at 4 of 44 sites. Further analysis revealed critical environmental factors influencing distribution, primarily dissolved oxygen concentration and the presence of physical barriers such as hydroelectric stations. Our data suggest a minimum dissolved oxygen tolerance threshold of 4 mg/L for this species. Moreover, we observed an inverse relationship between detection rates and both the number of hydroelectric stations and their distance to sampling sites. This case study demonstrates the effectiveness of eDNA technology in mapping the distribution of endangered fish species like and guiding conservation strategies. Our findings emphasize the crucial need to enhance environmental conditions, particularly water quality and habitat suitability, to ensure the effective conservation of within the YUFRR.