An approach to intercalibrate ecological classification tools using fishin transitional water of the North East Atlantic

tA simple procedure to harmonise and intercalibrate eight national methods classifying the ecologicalstatus using fish in transitional waters of the North East Atlantic is described. These methods were initiallyintercalibrated and a new method recently developed was added to this exercise. A common humanpressure index pre-classified the status of each water body in an independent way. Ecological classboundaries values were established according to the level of anthropogenic pressure using regressionanalyses. A simulated dataset was used to assess the level of agreement between the fish classificationmethods. Fleiss’ multi-rater kappa analysis indicated that boundary harmonisation was achieved; allclassifications fell within one class of each other and class agreement between methods exceeded 70%.The use of a pressure index to establish boundary thresholds provides a practical method of defining andharmonizing the quality classes associated with human pressures, as required by the European WaterFramework Directive.