Movie 1

First, we show an example and summary of each step in processing for a typical decision.
Segment A. First, we start with the raw video of the fish movement corresponding to figure 2A. To minimize processing time, we select a clip just prior to the fish’s action. Segment B. We then select the region of interest for all frames of the video, and increase contrast. The median of these frames is used as a reference image background image for the rest of the image processing. Segment C. We then carry out frame by frame comparison of the median of the current frame against the background reference (e.g. median) frame. This results in a frame by frame highlight of places in which the image deviates from the reference, which correspond to the fish (clear shapes against a black background). Segment D. Standard deviation from the beginning to each frame time, for each spatial pixel of the movie described in segment C. Because the background/stationary areas have a small standard deviation, they are shown in black, and the clear regions correspond to high values of standard deviation caused by the presence of the fish. Segment E. The final step is to layer the movement of the fish on top of the field (as calculated by a finite element model, Caputi et al. 1998). This shows how the fish uses the field to orient itself during exploratory movements, and decisive approaches.