A new stereophotographic technique for analyzing the three-dimensional structure of fish schools

SynopsisA technique using two downward-directed 35 mm cameras has been modified to measure the three-dimensional structure of fish schools. The resulting stereo pairs of photographs are analyzed, producing the 3-coordinate location of each fish's nose, after correction for lens distortion and refraction. Separation angles (bearing and elevation) and distance can then be determined for any pair of fish in the school. The technique's high level of accuracy is demonstrated for an underwater calibration field. It is then applied to the measurement of the 3-D structure of schools of coho salmon (Oncorhymchus kisutch) swimming in a hatchery trough. Although the fish were not organized in a rigid crystal lattice, the analysis provided some evidence of structure.

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