Data Supplements

Supporting material for this study includes 3 videos and an algorithm code.

Files in this Data Supplement:

• Data Supplement - HTML-formatted version of the Matlab code used to measure current flow in current camera videos, with a full algorithm and parameter description. The original m-file and a sample video necessary to allow execution of the code in Matlab can be obtained from the corresponding author, Russell Wyeth (Russell.Wyeth@dal.ca)
• Movie 1 - Current camera video processing to generate flow measurements. Four versions of the same 5 s current camera video clip are shown at ½ speed.

  Top left: original video, cropped to the boundaries of the black metal sheet background (38 x 25 cm).

  Top right: enhanced motion version, showing the improved contrast of moving particles.

  Bottom left: final enhanced video (after threshold and particle shape filters were applied), showing particles (white) available for tracking.

  Bottom right: demonstration of the vectors used to generate the flow measurement. Each frame shows a sequential pair of frames from the final enhanced video: 1st frame particles (red); 2nd frame particles (blue). Shown in white are vectors linking particles between the frames that contribute to the mean heading calculated for the frame pair (central white arrow). Green vectors are those of similar length but rejected by the particle tracking velocimetry algorithm. The overall mean heading for the 5 s video clip is shown by the blue central arrow. Some frames are blank because of duplicated frames that cannot be used for tracking particles.

• Movie 2 - Particle tracking velocimetry algorithm can accommodate variation in flow. The frame-by-frame heading (white arrow) calculated by the algorithm matches the oscillating movement of the tracked particles (red) and, as a result, the true mean heading (red arrow) is calculated for this 5 s motion enhanced video clip. Frame dimensions: 38 cm x 25 cm.
• Movie 3 - Current camera flow measurements agree with video of a dye plume in cameras used to record Tritonia diomedea behavior. Flow, indicated by a dye plume produced from a fluorescein source near the top of the frame, consistently corresponds with the measurements made several meters away in a current camera (blue arrow). Also visible are several seapens, Ptilosarcus gurneyi (pt), that orient similarly to the flow, and several T. diomedea (td) that crawl through the field of view. 3 h video, 450 x speed.