A video analysis procedure for assessing vertical fish distribution in aquaculture tanks

Abstract

This paper describes an economical and efficient video analysis procedure for registering vertical fish distribution in aquaculture tanks. The procedure can be summarized in three steps: (1) A digital underwater camera is used to film a section of a tank wall marked with one or more vertical black lines. (2) Automatic image analysis is used to identify those parts of the lines that are not obstructed by fish in the individual image-frames. (3) The visible parts of the lines are compared with the known extent of the lines and the percentage coverage is calculated. The procedure does not require uniform or stable lighting conditions, only that the black stripes are clearly visible. A case study demonstrates that the procedure can be used to document how fish in a classical conditioning learning procedure react to a sudden fright stressor in the first trial and how the fish gradually become habituated to the stressor and start to associate it with feeding in subsequent trials. Since the procedure offers a good description of vertical distribution over time, is cost effective and easy to implement, we believe that it is likely to become a standard for describing fish behaviour in aquaculture tanks.