Acoustic ecological investigation of estuary habitat on Indo-Pacific humpback dolphin (Sousa chinensis) in Yunlin, Taiwan

A sunspecies/population of Indo-Pacific humpback dolphins (IPHD, Sousa chinensis) lives in the shallow waters of Eastern Taiwan Strait. Their habitat is very close to the coast and suffering from the impact of human activities and marine pollution; the survival of this vulnerable group is at high risk. The long-term visual survey result shows that the Xinhuwei estuary has been an IPHD hot spot. Two Passive acoustic monitoring (PAM) stations with temperature sensors were deployed to detect IPHD sounds in the estuary habitat. During the past four seasons, underwater marine recorders and temperature-depth data loggers were deployed at two locations in the estuary of Xinhuwei creek, Yunlin, Taiwan. The total duration of valid data for each station is at least 19 consecutive days during each season. IPHD's click-trains and whistles were counted by a supervised detection method. The results show that the trend of click-trains (echolocation and foraging sounds) is positively correlated with sea temperature. The most active foraging behavior occurs during the daytime of summer. Whistles (social and communication sounds) are most common during spring. Except in winter, the number of click-trains and whistles are larger at the deeper measuring station (water depth of 11 m). This research was funded by Formosa Petrochemical Corporation.