Acoustic and Visual Monitoring of Marine Mammals in the Southern California Bight

Goal: To collect baseline information on marine mammal behaviors in the Southern California Bight using both acoustic and visual methods. This information is being collected in order to better assess the potential effects of U.S. naval activities in the area.

Time Period: 2012

Our role: To develop and operate a portable, real-time sonobuoy system for monitoring the acoustic behaviors of marine mammals being observed, as well as others nearby. These data were recorded, analyzed, and integrated with the visual data collected concurrently by our project partners.

One of the primary goals of this project was to integrate real-time monitoring methods using both visual and passive acoustic methods from an airplane. Data were recorderd using digital video cameras and acoustic recorders so that they could be analyzed further via post-processing. To monitor marine mammal and anthropogenic sounds, sonobuoys were deployed from the belly window of an observation aircraft (Twin engine Partnavia). Sonobuoys allow sounds to be remotely telemetered via radio to a receiver on the airplane. Visual observations and videography of surface behaviors for focal whales were conducted simultaneously while monitoring and recording acoustic signals from the sonobuoys. Sonobuoys were deployed in both the low-frequency (2 kHz) directional (DIFAR) mode as well as the mid-frequency (20 kHz) omni-directional mode.

Using these integrated methods, we acoustically detected and recorded sounds from groups of fin whales, gray whales, humpback whales and bottlenose dolphins and Risso’s dolphins. Using data from DIFAR mode sonobuoys, bearings were plotted to animal calls in real-time for some focal animal groups. During post-processing, we were able to integrate visually estimated animal locations with acoustically determined bearings and/or localizations. We determined that fin whales called frequently as they migrated northwards. Perhaps the most interest finding was counter-calling between fin whales that were widely separated (several km’s to tens of km’s) dynamic groups. The integration of visual and passive acoustic data will help to increase our understanding of marine mammal behaviors by providing more complete information to interpret behaviors of marine mammals in relation to anthropogenic activities.

Collaborators: Smultea Environmental Sciences, Texas A&M University at Galveston

Sponsor: HDR (Prime), NAVFAC-Southwest Div. (NAVFAC SW)

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