Telemetry Study on Juvenile Yellowfin Tuna Thunnus albacares Around a Payao in the Philippines

摘要

Three juvenile yellowfin tuna (22-26cm FL) and two rainbow runners (27 and 30cm FL) were monitored around a payao (FAD: Fish Aggregating Device) in Panay Gulf, the Philippines. A receiver was attached to the anchor line of the payao and ultrasonic transmitters were implanted into the abdominal cavities of the fish. All the fish stayed around the payao for over 60 hours and there was no difference in the hourly detection rate during daytime and nighttime. Juvenile yellowfin tuna were swimming in significantly deeper waters, maximum 105m, than rainbow runners of the same size. The similarities between the observed behaviors of payao-associated juvenile yellowfin tuna and FAD-associated adults are very striking. Juvenile yellowfin tuna swam within a limited shallow range during nighttime and dived to deeper waters during daytime then moved away from the payao at midnight. One juvenile yellowfin tuna was recaptured two days after release by hand line in the same payao and two juvenile yellowfin tuna were recaptured 12 days after release by ring net in another payao over 3km away. These recaptures indicate that the fish were active enough to feed and swim, and also show the feasibility of undertaking telemetry studies on juvenile yellowfin tuna.