In-Situ Investigation of Copepod Predators of Theronts from Fish-Farming Pond.

, a parasitic ciliate, causes "white spot disease" in freshwater fish and poses a significant threat to global freshwater aquaculture. Eliminating the free-swimming theront stage from the aquaculture environment is a critical measure for controlling infections. The natural predator of theronts in fish-farming ponds were identified using fluorescent dye-labelled live theronts and quantitative PCR; meanwhile, the zooplankton community composition in the positive ponds of detected by quantitative PCR were analyzed by eDNA metabarcoding assay. The results revealed predation on theronts by cyclopoid copepods, including , , sp., sp., sp., and sp. from the in-situ predation aquatic ecosystem, and among these copepods, was identified as a natural dominant predator of . This study provides a scientific basis for further exploration and utilization of natural predators to enhance sustainable and environmentally friendly control strategies against .