Passive acoustic monitoring of biological activity on coral reefs and in nearby waters

• Published in: The Journal of the Acoustical Society of America 2005-09, Vol.118 (3_Supplement), p.1908-1908
• Main Authors: Lammers, Marc O., Mooney, T. Aran, Brainard, Russell E., Au, Whitlow W. L.
• Format: Article
• Language: English
• Subjects: Cetacea; Crustacea; Marine
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4780155

Monitoring the changing state of coral reef habitats is a challenging task that is exacerbated when the reefs in question are in remote locations. Physical sensors provide a wide range of measurements of local environmental variables, but do not give an indication of biological activity. The preliminary findings of an effort to use the ambient sound field as a means of characterizing and monitoring biological activity on coral reefs and surrounding waters are reported. Moored recording systems were developed to sample the sound field of reefs on Oahu, Hawaii for 1-min periods, at 30-min intervals, for 10 days at a time. Snapping shrimp produce the dominant acoustic energy on the reefs examined and exhibit clear diel acoustic trends. Peaks in activity consistently occur during crepuscular periods. At frequencies below 2 kHz, many fish sounds occur, which also exhibit distinct temporal variability. Cetacean sounds are also common, indicating the occurrence of an apex predator in the area. Many sounds can be detected automatically, making the examination of the sound field an efficient means of tracking acoustically active species. The results indicate that acoustic monitoring may be an effective means of tracking biological activity at locations where traditional surveys are impractical.