Environment DNA reveals fish diversity in a canyon river within the upper Pearl River drainage

At each sampling site, 2 L of water samples were collected using a water collector positioned approximately 0.5 m below the water surface in August 2022. Three replications were conducted at each sampling site. Prior to sampling, water samplers and sampling bottles were disinfected with 10% bleach powder solution, and sampling personnels change disposable gloves after each collection. To prevent DNA degradation, the water samples were promptly stored in cold storage and filtered using a vacuum pump onto a 0.45 Micrometre mixed cellulose filter membrane (Whatman, UK) within 12 hours. The vacuum pump was sterilized and rinsed before each sample filtering to prevent cross-contamination. Subsequently, the filter membranes were promptly transferred into sterile 4.5 mL plastic scintillation tubes and rapidly stored in liquid nitrogen in the field. Finally, the filter membranes were preserved at -80 degrees Celsiusin the laboratory until DNA extraction.