An evaluation of active acoustic methods for detection of marine mammals in the Canadian Beaufort Sea

A commercially available fisheries sonar was mounted on an icebreaker and evaluated during an environmental baseline study in the Canadian Beaufort Sea, to determine the applicability of active acoustic monitoring ( AAM ) for marine mammal detection by comparing marine mammal observer ( MMO ) visual sightings and active acoustic detections. During 170 h of simultaneous MMO and AAM , 115 bowhead whales ( Balaena mysticetus ) and four beluga whales ( Delphinapterus leucas ) were visually sighted by MMO s, while 59 sonar detections of bowhead whales occurred using AAM . The fisheries sonar detected 92% of the cetaceans observed within 2,000 m. Additional observations of ringed seals ( Pusa hispida ) and bearded seals ( Erignathus barbatus ) were recorded both by MMO s and AAM . Comparative results indicate that a commercially available active acoustic system can consistently detect marine mammals within varying ranges dictated by water column properties. Shallow environments and strong pycnoclines currently present challenges to AAM .