Many ecological variables show a wide range of fluctuations, the most important of which is the diurnal variation. This cycling may contain important information regarding the ecosystem’s functioning and, if properly interpreted, can represent a valuable predictive tool in ecosystems management. This paper describes a simple algorithm for extracting meaningful information from daily cycles using fuzzy pattern recognition techniques. The algorithm is organised in three parts: in the first, typical patterns are extracted from experimental data to form the knowledge-base upon which the algorithm operates. The second step is to condense the information contained in the knowledge-base into mathematical objects, referred to in the paper as fuzzy masks. The third step is the set-up of an inferential set of fuzzy rules, using the fuzzy masks as antecedents. Depending on how the inference engine is structured, the algorithm output can be viewed as an assessment of the current daily cycle ...