Effect of Deep-Water Multibeam Mapping Activity on the Foraging Behavior of Cuvier’s Beaked Whales and the Marine Acoustic Environment

Hilary Kates Varghese

Doctoral Dissertation Defense
Earth Sciences – Oceanography

Tuesday, Nov. 23, 2021, 10:00am
RDML Rick Brennan Conference Room - Chase 210

Mid-frequency (< 10 kHz) acoustic sonar, used in naval training exercises, is known to adversely affect sensitive marine mammals. Less is known about the effects of higher frequency sonar sources (>10 kHz)  such as multibeam echosounders—on marine mammals. To date, no controlled studies have been conducted to evaluate the effect of multibeam echosounders (MBES) on marine mammals in the wild, despite the widespread use of this sound source in scientific research and geophysical work. Here the temporal and spatial effect of deep-water MBES signals on Cuvier’s beaked whale foraging behavior was assessed during two deep-water MBES ocean mapping surveys of the Southern California Antisubmarine Warfare Range (SOAR). The SOAR contains an array of 89 hydrophones spanning an 1800 km2 area that was used to detect echolocation clicks from foraging beaked whales during the mapping surveys. The acoustic data from the array was also used to assess and characterize the change in sound levels of the marine acoustic environment during one of the MBES ocean mapping surveys.

Hilary's advisor is Dr. Jennifer Miksis-Olds and her committee members are Dr. Larry Mayer, Dr. Xavier Lurton, Dr. Kim Lowell, and Dr. Thomas Lippmann.


Hilary Kates Varghese holds a bachelor’s degree in biological science with distinction in research from Cornell University, and a master’s degree in applied mathematics from Florida Gulf Coast University. Hilary worked in the algal biofuel industry as a researcher before pursuing a Ph.D. in earth sciences-oceanography at the University of New Hampshire, focused on the effect of sound on marine life. Her eclectic interests and experience in renewable energy, biology, and acoustics have aligned her well for her next chapter as a bioacoustician in the Center for Marine Acoustics with the Bureau of Ocean Energy Management.