A quantification of goldfish behavior by an image processing system.

We developed a computer-image processing system to quantitatively score the goldfish behavior. The system was composed of two CCD cameras, set in the upper and side directions of a water tank, two graphics I/O boards (video interface) and an IBM PC/AT compatible computer. From the top and side views through the two CCD cameras, 2-dimensional or 3-dimensional positional coordinates of fish freely moving in an aquarium were acquired over a long period (60 min). A positional distribution histogram of the goldfish was made by measuring the number of coordinates. Goldfish have a tendency to move at the circumference and bottom of a water tank. The velocity of moving goldfish was calculated from the time and distance. The average velocity of goldfish was in the range of 6-36 mm/s. A directional histogram (go straight and turn right or left) of a moving goldfish in an aquarium was made to measure an angle formed by two vectors, which were defined as three (middle to terminal against initial to middle) points in a unitary length (50 mm) of the path of goldfish. Three directions (go straight, right turn and left turn) were quantified as a percentage (59 +/- 12%, 20 +/- 4% and 20 +/- 4%, respectively) of a 1-h-event of moving goldfish. This image processing system thus can make an easy and quantifiable behavioral analysis of moving goldfish.