Acoustical and visual monitoring of the discharge process of the last captive Indo-Pacific Bottlenose Dolphin in South Korea

Abstract

The discharge of Bibong, a 23-year-old Indo-Pacific Bottlenose Dolphin, marked the end of its 17-year aquatic show life in an aquarium on November 16, 2022. The three-month adaptation training included a temporary retreat due to typhoon HINNAMNOR. To continuously capture underwater sound, two hydrophones were alternately used due to limited operation time. Additionally, two CCTV cameras and two drones were employed to record events around the discharge cage, with one observer per drone. Using a CNN-based whistle profile extractor, whistle sounds were automatically detected and exported as time-stamped data. The corresponding CCTV and drone clips were examined for each whistle encounter. Our study presents the whistle sound encounter pattern and the synchronized acoustical and video data. These findings offer valuable insights into understanding the discharge process, serving as a reference for future discharge initiatives and welfare assessments of captive marine mammals.