DESCRIZIONE
A method for external fish parasites, such as sea lice, monitoring in aquaculture, comprising the steps of: - submerging a camera (52) in a sea pen (40) comprising fish (72, 74); - capturing images of the fish (72, 74) with the camera (52); and - identifying external fish parasites such as sea lice on the fish (72, 74) by analyzing the captured images, characterized by the steps of: - distinguishing between at least two different classes of external fish parasites such as sea lice which differ in the difficulty of recognizing the external fish parasites such as sea lice; - calculating quality metrics for each captured image, the quality metrics permitting to identify the classes of external fish parasites such as sea lice for which the quality of the image is sufficient for sea lice detection; and - establishing separate detection rates for each class of sea lice, each detection rate being based only on images the quality of which, as described by the quality metrics, was sufficient for detecting external fish parasites such as sea lice of that class.