Method for monitoring stress in a sample of a fish and/or a fish culture

The invention is based on the detection of stress markers in a sample of fish and/or a fish culture, such as an aquaculture water sample. Specifically, the invention provides a method for monitoring fish stress and evaluating fish health in an automated manner. In one aspect, the invention pertains to a method of identifying, predicting, monitoring, and/or diagnosing a stress in a fish and/or a fish culture, wherein a differential level of at least one nucleic acid in the sample compared to a reference sample or reference value or a time-dependent change of the at least one nucleic acid in the sample is indicative for the stress in the fish and/or the fish culture. Further provided is a method of stratifying a fish and/or a fish culture for a culture condition, and a kit for performing a method according to present invention. The invention also pertains to the use of at least one nucleic acid as an indicator for a stress in a fish and/or a fish culture.