Cetacean behavior in relation to oceanography, prey, and mid-frequency active sonar
Abstract
Cetacean behavior in relation to oceanography, prey and mid-frequency active sonarPROJECT SUMMARYMarine mammals, particularly beaked whales and endangered baleen whales are of concern to the US Navy regarding noise impactsduring naval training exercises using mid-frequency active sonar (MFAS). To successfully quantify behavioral responses to MFAS and potential short- and long-term impacts, it is essential to understand the behavior of individuals under natural as well as disturbedcircumstances. The aim of this proposed work is to investigate the fine-scale dive behavior of Cuvier#s beaked whales (Ziphius cavirostris) as well as blue whales (Balaenoptera musculus) and fin whales (B. physalus) in relation to measured prey distributions and environmental variables at a highly sonar-impacted and a minimally disturbed site. Marine mammals inhabit a highly dynamic, mobile environment. Unlike terrestrial or benthic habitats, pelagic habitats are influenced by fluid dynamical features that change positionand structure over time. This presents a challenge for management and conservation. We will test the following hypotheses: (1) Local physical oceanographic conditions drive small-scale epi-, meso-, and bathypelagic prey distributions. (2) Marine mammals # with a focus on blue, fin, and Cuvier#s beaked whales # sense and target dense aggregations of prey and adapt their foraging behavior to changing prey conditions. (3) Use of MFAS during US Navy training operations will invoke a behavioral response, in the form of quantifiable change in marine mammal acoustic and dive behavior. (4) The behavioral response will be dependent on the underlying prey conditions and the current behavioral state of the individual.Data collection occurred with multi-channel passive acoustic recorders at asonar-impacted and a minimally disturbed site. These will be analyzed to identify tracks of calling blue and fin whales and track fine-scale dive behavior of Cuvier#s beaked whales during foraging. Information on pelagic prey was collected with autonomous active-acoustic systems. Physical oceanographic features were measured with autonomous conductivity-temperature-depth (CTD) and oxygen sensors. Blue, fin and Cuvier#s beaked whale tracks will be computed across a 2-year data set based on their B, D, 20 Hz and 40 Hz calls, and echolocation clicks, respectively. MFAS occurrence will be documented. Active acoustic backscatter strength of taxonomic groups will be integrated across relevant depth bins. Physical oceanographic properties will be computed across those depth bins. A statistical framework will be developed to test relationships.Dynamic ecosystem-based management and impact mitigation requires a holistic view of the pelagic ecosystem, with an understanding of not only organismal behavior but also of the underlying physics. This workwill provide insight into the physical drivers of nekton distribution from surface waters to the bathypelagic and the subsequent marine mammal response at a sonar-impacted and minimally disturbed site in comparison.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 15, 2023
- Source ID
- N000142312435
Entities
People
- Simone Baumann-Pickering
Organizations
- Office of Naval Research
- United States Navy
- University of California, San Diego