Fine-scale Foraging Behavior of Marine Mammals in Relation to Oceanography, Prey and Mid-frequency Active Sonar
Abstract
Marine mammals, particularly endangered baleen whales and beaked whales are of concern to the US Navy in regard to noise impacts during naval training exercises. To quantify and mitigate the impact of noise on marine mammals, it is essential to understand the influence of the physical marine environment on the distributions of marine mammals and their prey. The aim of this proposed work is to compare foraging and diving behavior of blue, fin and beaked whales at a sonar-impacted and a minimally disturbed site within the Southern California Bight, using data on oceanography, prey, cetaceans and mid-frequency active sonar (MFAS). Marine mammals inhabit a highly dynamic, mobile environment. Unlike terrestrial or benthic habitats, pelagic habitats are influenced by fluid dynamical features that change position and 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 Cuviers 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. An experiment will be conducted to record multi-channel passive acoustic data at a sonar-impacted and a minimally disturbed site to identify tracks of calling blue and fin whales, and track fine-scale dive behavior of Cuviers beaked whales during foraging, respectively. Information on pelagic prey will be collected with autonomous activeacoustic systems. Physical oceanographic features will be measured with autonomous conductivity-temperature-depth (CTD) and oxygen sensors. Blue, fin and Cuviers beaked whale tracks will be computed across the 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 work will 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
- Aug 31, 2020
- Source ID
- N000142014000
Entities
People
- Simone Baumann-Pickering
Organizations
- Office of Naval Research
- United States Navy
- University of California, San Diego