Abstract: A method for recording and estimation of the weight of fish. A number of cameras, especially CCD-cameras, record pictures of fish moving by the cameras in a transfer conduit. The fish is illuminated from different sides in the transfer conduit and pictures of different parts of the fish are recorded by a sequence control, in such a way that a compound image recording is made, which is used as a base for an estimation of the weight of fish. A device to make measurements on fish 11, moving in a transfer conduit 12, that has at least two light sources 14 at the wall of the transfer conduit, for illumination of fish, and two or several cameras 10, especially CCD-cameras, arranged in a cross plane evenly around the circumferences, to record reflections from the fish or shadow pictures of the fish.