OBSERVING FISH USING UNDERWATER CAMERA AT THE TEST SITE BEFORE INSTALLING OCEAN POWER GENERATION

摘要

Assessment of local ocean environment is significant when devices of marine renewable energy are installed at a demonstration site. A concern about how these devices affect the existence of fish is remained among local fishermen. To confirm variation of fish before and after installing the devices of marine renewable energy, we investigated fish using an underwater camera before installation as a main objective of this paper. First, fish-eye video camera was tested to monitor in a fish cage off Kamaishi city, Iwate prefecture, Japan. We aimed to observe the abundance of fish and to specify the species of fish. The fish-eye video camera is composed of a dome-shaped lens, a container, and a digital video equipped into the container. The recorded video showed outlines of fish, consequently it may be possible to know the abundance of fish. However, specifying the species of fish has a difficulty if we use fish-eye camera since the recorded image is unclear enough to identify correctly. In addition, we examined horizontal transparency of fish-eye camera using a fish-shaped target. Before recording by the video camera, vertical transparency was measured using a white plate. Then we recorded the images by varying the water depth and the distance between the camera and target. When the target was close to the camera, it can be displayed clearly, nevertheless the outline of the target was smeared with increasing the distances between them. Our measurement suggested that the horizontal transparency might be relating to the parameters of water depth and vertical transparency. The investigation was conducted under the one condition, thus we need to obtain further data to understand horizontal transparency qualitatively. Next time, we will conduct another test using additional underwater optical video camera, which is attached on the fish-eye video camera. The combination of these two types of video cameras may enable to observe the abundance of fish as well as to specify the species of fish.