FIRST RECORD OF SPERM WHALE DETECTION USING A HYDROACOUSTIC INSTRUMENT IN THE VICINITY OF FISH AGGREGATING DEVICES (FADs) IN THE MOLUCCA SEA

Knowledge of the occurrence and behaviors of formerly intensively exploited marine mammals, such as sperm whales and around fish aggregating devices (FADs) are lacking yet crucial for guiding species conservation management. FAD-based fisheries attract targeted fish such as tuna and Endangered-Threatened-Protected species like sperm whales, making these species more vulnerable. Acoustic studies are imperative to learn more about sperm whale’s ecology. This study aimed to investigate the occurrences and activity patterns of sperm whales around FADs using active acoustic methods in the Molucca Sea. The 200kHz echosounder instrument was employed in this study to measure the target strength (TS) based on vertical movement patterns in the echogram. The presence of sperm whale has been observed spending around 6 hours at shallow depths during daylight over 10 days near the FADs, with depths varying from 0 to 50 meters. The temporal variations in the scattering amplitude (SA), with the highest SA values observed between 10:00 AM and 5:00 PM. The TS values were measured at -31dB, 34dB and -30dB for the head, tail and broadside aspects, respectively. The findings from this study are anticipated to offer crucial contributions to the ecological understanding of sperm whales, thereby establishing a foundation for more effective conservation and management efforts within the Molucca Sea.