In this study, we developed a measurement method for the total length of white spotted conger eel Conger myriaster, caught with conger eel tubes, by using video images. In case of conger eel, the total length fails to measure the length of the line which was connected the snout and the end of the caudal fin, because conger eel swims meandering. To solve this problem, we made some points of division between the snout and the end of the caudal fin, and measured the length of the line connecting each point. The relation between the number of points and measurement accuracy was examined and this method was developed to a practical level with over eight points and a correction factor. This method was applied to an actual fishing operation, and 97% of total catch was measured without handling conger eel directly. Additionally, it could arrange a total length distribution every location by adjusting fishing location.
