Development of wide-area and long-term tracking system for skipjack tuna Katsuwonus pelamis around FADs

Skipjack tuna Katsuwonus pelamis is known to aggregate around fish aggregating devices (FADs), and many ultrasonic biotelemetry investigations have been conducted around FADs. However, the investigation areas have been limited to the area around surface type FADs where receivers can be installed, and adequate tracking cannot be achieved. To clarify the behavioral ecology of skipjack in more detail, it is necessary to carry out extensive and long-term observations. We have developed a fishing boat-mounted receiving system that combines an ultrasonic biotelemetry receiving system and a data communication terminal. The developed system was installed on a fishing boat that operated around FADs in waters around Yonaguni Island, Okinawa, Japan, located in the upper Kuroshio Current. The effectiveness of behavioral investigation of skipjack around FADs was verified. As a result, we were able to expand the tracking area and received the locations of individuals by GPS and successfully tracked them for long periods. Furthermore, data were collected in an efficient manner by using an information and communication technology (ICT) network as a data acquisition method.