Passive Acoustic Monitoring (PAM)

The Rockhopper – Marine Passive Acoustic Recording Unit

The Rockhopper is a new passive acoustic recording unit developed by Cornell’s K. Lisa Yang Center for Conservation Bioacoustics (see picture below). The unit is primarily used to listen for and record the sounds of marine mammals (and fish), which regularly produce species-specific sounds underwater. A primary design goal was to significantly reduce the cost associated with long-term acoustic data collection in offshore, deep-water ecosystems. While U.S. coastal waters have been comparatively well studied, large knowledge gaps exist on the abundance and distribution of cetaceans beyond the continental shelf.   

The Lithium-battery powered recorder is small — the main electronics are housed in a 17-inch glass sphere — and can be deployed and recovered by one person without the aid of a hydraulic winch or A-frame. In addition, all mooring components have a maximum deployment depth of 3,500 m, ideally suited for deep water. Finally, the Rockhopper can be programmed to record frequencies in the 10 Hz to 150 kHz range, covering the frequency range of all known marine animal sounds. Note the human hearing roughly covers the 20 Hz to 20 kHz frequency range. However, marine mammals are known to produce sounds in the infrasonic (< 20 Hz; e.g., blue whales) and ultrasonic (>20 kHz; e.g., beaked whales) ranges, both outside of human hearing ranges. Hence, we rely on specialized recording equipment for our marine monitoring efforts.

We will initially focus on the frequency range 10 Hz to approximately 80 kHz for the HALO project. This will allow us to record all species of interest except for Harbor and Dall’s porpoises. During a typical 6-month deployment, each Rockhopper will collect approximately 9 TB of uncompressed acoustic data!

We are planning to deploy a total of three units off Newport, OR. One will be deployed on the continental shelf (25 nm offshore), one at the shelfbreak (45 nm offshore), and one on the abyssal plain (65 nm offshore). These deployment locations represent very different environments with different oceanographic conditions.

Klinck, H., Winiarski, D., Mack, R. C., Tessaglia-Hymes, C. T., Ponirakis, D. W., Dugan, P. J., Jones, C., & Matsumoto, H. (2020). The Rockhopper: a compact and extensible marine autonomous passive acoustic recording system. Global Oceans 2020: Singapore – U.S. Gulf Coast, 1–7.