Automated three-dimensional measurement method of in situ fish with a stereo camera

An acoustic-optical integrated measurement deep-tow system called J-QUEST (the Japanese quantitative echo sounder and stereo-video camera system), consisting of a quantitative echo sounder and two synchronized cameras, has been developed for the observation of mesopelagic fishes such as lanternfish by the Fisheries Research Agency, Japan. The quantitative echo sounder is designed for measuring fish target strength and assessing the fish abundance, and the optical cameras are aimed for identifying fish species, measuring fish tilt angle distribution, counting and sizing fish that passing through the camera views. In order to obtain the distributions of fish length and tilt angle, a commercial-release optical image processing software has been used so far. However, the measurement, which has to be carried out frame by frame manually, is time-consuming and labor intensive. This paper presents a fully automated three-dimensional method to measure in situ fish using image pairs taken by the two cameras.