ACOUSTIC MONITORING OF ECHOLOCATING PORPOISES

摘要

Underwater ultrasonic sound of finless porpoises Neophocaena phocaenoides were monitored concurrent with visual observations in the Yangtze River, China. In a total of 774km cruise, 588 finless porpoises were sighted by visual observation and 44,864 ultrasonic pulses were recorded. The acoustic monitoring system could detect presence of the finless porpoises 82% of the time. False alarm in the system occurred with a frequency of 0.9%. The high frequency acoustical observation is suggested as an effective method for field surveys of small cetaceans, which produce high frequency sonar signals.