Using passive and active acoustics to examine relationships of cetacean and prey densities
Abstract
Ambient sounds from long-term passive acoustic recordings show a diel and lunar pattern. Preliminary analysis suggests that backscatter organisms in the water column, possibly from deep-scattering layer (DSL) organisms, either produce sound or modulate the propagation of sound based on diel changes of their depth distribution and density. Ambient sound patterns of biological origin in a frequency range relevant to US naval sonar may alter sonar ranges with predictable patterns. Additionally, organisms in the water column are “bio-clutter” targets that alter sound propagation on these time scales, dependent on the target behavior and density. The goal of the proposed project is to identify if sound is produced or modulated by backscatter organisms and to describe the long-term variability of these sounds based on fixed sensors. In conjunction with this we will use active acoustic data from a variety of sources to document variability of acoustic backscatter on similar temporal scales but also with spatial respect in both depth and along horizontal survey lines. We will investigate the relationship of intensity of acoustic backscatter and ambient sound across time and space. These results will be relevant to the US Navy sonar community. Scatterer, especially krill and DSL organisms, are prey items for large predators, of which marine mammals are of particular interest to the US Navy. Predator-prey relationships are important ecosystem drivers. Prey is likely a good indicator for marine mammal distribution, abundance, and behavior. Moving models on cetacean dynamics from distant indicators (such as chlorophyll or temperature) to actual prey measures is an intriguing opportunity. Cetacean acoustic detections will be noted on passive acoustic data. We will identify if acoustic backscatter and ambient noise measurements may be suitable for predictive modeling of cetacean presence. The possibility of long-term, autonomous monitoring of prey distribution and behavior using passive acoustic means will lead to an increased predictability of marine mammal presence in an area relevant to the US Navy.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512587
Entities
People
- Simone Baumann-Pickering
Organizations
- Office of Naval Research
- United States Navy
- University of California, San Diego