Acoustic Monitoring Studies

Passive acoustic monitoring of biological & anthropogenic activities

M. Lammers & W. Au

An EAR deployed on a coral reef (NOAA).

The use of passive acoustic tools to record biologically produced sounds in aquatic environments is becoming a tool of choice for assessing and monitoring biological activity in habitats where conventional survey methods are impractical or not cost effective. This is because many species of fish, invertebrates and marine mammals regularly produce sounds for communication, displaying and/or environmental sensing. In addition, acoustic monitoring is also an effective means of detecting human activities in a marine habitat, such as vessel traffic and explosives used in fishing. Passive acoustic monitoring can therefore provide a cost-effective means of logging both biological activity and human presence at a location and thus help gauge the effectiveness of management practices.

The occurrence of humpback whale song.

The Ecological Acoustic Recorder (EAR) is a digital, low power acoustic recording system designed to sample the ambient sound field. Preliminary findings reveal that the recorded Pearl and Hermes Atoll (PHA) location had the highest noise level measured by an EAR deployed in the Pacific, it is possible that the high acoustic energy characterizing this area may be tied to high levels of productivity in the water (Lammers et al, 2006). At French Frigate Shoals, dolphin and fish signals were common and, somewhat surprisingly, the song of humpback whales (Megaptera novaeangliae) was frequently recorded. One or more whales were recorded singing on 59 days, with the greatest frequency occurring between the end of February and March.

For more information visit: www.hawaii.edu/mmrp/

Recent papers related to this work

Lammers, M.O., Brainard, R.E. and Au, W.W.L., Mooney, T.A. and Wong K. (2008). “An Ecological Acoustic
Recorder (EAR) for long-term monitoring of biological and anthropogenic sounds on coral reefs and other marine habitats.” J. Acoust. Soc. Am. 123:1720-1728

Lammers, M.O., Brainard, R.E. and Au, W.W.L (2006). “Diel trends in the mesopelagic biomass community of the Northwestern Hawaiian Islands observed acoustically”. Atoll Research Bulletin, 543:391-407.

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