The present invention relates to a method for detecting the prone/supine position of fish (12) conveyed by means of a conveying device (13), comprising conveying the fish (12) by means of the conveying device (13) in the longitudinal direction (11) of the fish, optically scanning the ventral side (15) and dorsal side (16) of the fish (12) in pairs in order to determine a first brightness value profile of a first side and a second brightness value profile of a second side of one of the fish (12) in each case by means of optical scanning means (14), determining a first ordered data series and a second ordered data series by ordering brightness values of the first brightness value profile and of the second brightness value profile according to a predefined ordering criterion, determining a first median value from the first ordered data series and a second median value from the second ordered data series, determining at least one difference value from the first median value and the second median value, and determ
