Change of source level of pinger due to implanting into fish

The purpose of this study was to clarify the change of the source level (SL) of a pinger implanted in a fish and its influence on the receiving distance of an ultrasonic biotelemetry system. A nondirectional transmitter was implanted in three southern bluefin tuna instead of a pinger and the SL of the implanted transmitter was measured from various directions for each tuna. As a result, it was confirmed that the SL changed according to the direction. The maximum decrease of the SL was about 34 dB and the decrease in the receiving distance was estimated to be about 460 m. Our results suggest that the SL and the receiving distance are decreased by implanting a pinger in a fish.