Satellite radio tracking of bottlenose dolphins Tursiops truncatus

Satellite-linked radio tags were attached to 14 bottlenose dolphins in order to investigate the migration, movement, and behavior of the bottlenose dolphin. Eleven of the 14 tagged dolphins were released in Katsumoto, Iki Island, and Taiji, Kii Peninsula, from 1983 through 1986. The ARGOS satellite-baced data collection and location system was used to track the tagged dolphins. The movement of dolphins was related with sea surface temperature obtained from the AVHRR of NOAA 9. The contacts with satellite were made for the periods of 12 min to 35 days. One of the dolphins was tracked continually for 18 days and travelled about 604 km. The dolphin released off Katsumoto moved to the fishing ground of yellow tail and turned back near Iki Island. The radio tag slipped off the dolphin and was recovered on the shore. Two dolphins released off Taiji in different years swam along the Kuroshio Current toward the southeast on a similar route. This movement appears to be one of the migration routes of the bottlenose dolphins which occur off Kii Peninsula in spring. One of the other dolphhls passed through the same area three times on different days. The average speeds of the tagged dolphins which swam actively over 2 days were 34.2 to 45.9 m/min, and the maximum speeds were 106.4 to 123.7 m/min. The dolphins tended to swim faster between midnight and sunrise. The location accuracy of the radio transmitters attached to dolphins seemed to be within about 3.5 km. The location was made at about 50% of the contacts with satellite, and 5 to 6 times a day.