Fish eRNA: water sampling and filtrationthrough Sterivex filter unit v1

The objective of this protocol is the sampling and the filtration of water samples through 0.45 µm Sterivex™ filter units with the necessary precautions for environmental RNA (eRNA) analysis. This protocol is used upstream to molecular biology analysis (e.g. qPCR, metabarcoding, ddPCR) to specifically target fish eRNA. eRNA is easily degraded, so special precautions must be taken. These include: limit RNase contamination by working with decontaminated equipment, proceed very quickly to filtration after sampling, and freeze the samples very quickly after filtration, either in liquid nitrogen or in a freezer at -80°C. Preservation buffers are available to stabilise RNA at room temperature, but are not used in this protocol. This protocol allows approximately 0.5 L to 5 L to be filtered through a Sterivex‱ filter unit, depending on the characteristics of the water sample and the chosen filtration method (syringe or vacuum pump).