Autonomous Floating Acoustic Array and Tags for Cue Rate Estimation
Abstract
The ability to estimate marine mammal densities is crucial for estimating the impacts of US Naval activities on their populations. Passive acoustic methods have been successfully used for density estimation, however the knowledge of the average call production rate (cue rate) is often the limiting factor in obtaining the final density estimate. Cue rate estimation has been conducted from acoustic tag data as well as concurrent visual and acoustic survey where number of signals produced can be directly linked to the number of animals in the group. Part of the challenge in using acoustic tag data to calculate cue rate is that generally, there is no clear way to determine whether sounds recorded on a tag are produced by the tagged animal, or may be coming from a nearby animal. Additionally, some species are simply difficult to approach and tag in the first place. A possible alternative method would combine visual and acoustic tracking of groups of animals over time, to provide statistics on calling behavior of groups, leading to a cue rate estimate. To link the number of animals to call production rates, a new autonomous floating acoustic array will be developed based on Drifting Acoustic Spar Buoy Recorder (DASBR) developed by Dr. J. Barlow. The original DASBR will be modified for low-frequency signal and it will consist of a spar buoy with internal transmitting GPS, a SoundTrap STD 300 recorder with a HTI-96-MIN hydrophine suspended at approximately 25m depth. The LF-DASBRs will be compact, lightweight, easily deployable and retrievable from small or large vessels, and able to withstand a variety of conditions. To collect data needed for cue rate estimation, a six-element autonomous floaring passive acoustic array, consisting of six LF-DASBRs, would be deployed during focal follows of baleen whales to collect call production rate data. A pinger deployed on a separate float will be used to ensure LF-DASBR recorder clocks can be synchronized for localization of whale signals. Deployment of acoustic arrays will allow localization of all recorded calls in the vicinity of group of whales that is tracked via focal follow. These combined data sets will yield a count of calls produced by a group of a known number of animals over a certain time period, which ultimately will allow calculation of the average individual call production rate (cue rate). The instruments will also support research projects and teaching at Texas A&M University Galveston. Through the use of this equipment, undergraduate and graduate students and will get training in a variety of acoustic methods and techniques.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 13, 2019
- Source ID
- N000141912398
Entities
People
- Ana Sirovic
Organizations
- Office of Naval Research
- Texas A&M University at Galveston Bookstore
- United States Navy