Relationship between blue, fin, and beaked whales and their prey in Southern California
Abstract
The Southern California Bight (SCB) is a highly productive system due to seasonally strong upwelling conditions, which attract diverse megafauna including a large variety of cetaceans. It is also an area of high importance to the U.S. Navy with training ranges occupying a large fraction of the SCB. Understanding the occurrence and distribution of endangered and sensitive cetaceans in this area is of great importance to Navy operations.We propose deployment of two acoustic moorings in the SCB between October 2021 and October 2022. One mooring would be deployed at a location between Tanner and Cortes banks, approximately 100 mi offshore San Diego, whilethe other mooring will be switched between two locations, with 6 month deployment at each location. The moorings will consist of a passive acoustic recorder and two active acoustic systems. The passive component is a bottom mounted High-frequency Acoustic Recording Package (HARP) to record cetacean signals. The HARP will record continuously at 200 kHz sampling rate, providing an effective bandwidth from 10 Hz to 100 kHz. This is sufficient bandwidth to monitor the full acoustic repertoire of cetaceans likely to occur in this area, including both baleen whales and beaked whales. The active systems are Simrad Wideband Autonomous Transceivers (WBAT). Oneof the WBATs will be deployed with 70 kHz transducer looking upward at full mooring depth (~1000 m) while the other will have 70 and 200 kHz transducers and positioned at approximately 300 m depth, also upward looking. The shallow WBAT will provide estimates of euphausid and other plankton abundance in surface waters, while the deepone will record backscatter from squid and other deep water fauna. We will couple mooring data with net tows and synoptic ship-based echosounder surveys to evaluate contribution of different plankton taxa to the backscatter signal.The relationship between cetaceans and their prey will be investigated from this temporally extensive data set by applying the generalized additive modeling framework. In addition to the prey metrics from the active acoustic data, environmental data from in situ SeaBird microCATs and oceanographic variables available from a 3D ocean circulation model available for Southern California, remotely sensed surface variables, and a number of temporal variables, such as time-of-day, month, season, and year on the distribution of these whales will be used in model development. These models will provide information on functional relationships between these cetaceans and their prey.Understanding of cetacean-prey relationships is important for the Navy as it cross-cuts different relevant themes. Mapping of prey fields in relation to physical features and marine mammal distribution and behavior is one critical component that has been undersampled in many past studies of marine mammals. However, understanding those relationships provides critical context for interpreting behavioral responses to external stimuli(i.e. anthropogenic sound) as well as the development of predictive models of these species of concern. Additionally, this project will serve for training of future marine mammal scientists and oceanographers.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 05, 2021
- Source ID
- N000142112611
Entities
People
- Ana Sirovic
Organizations
- Norwegian University of Science and Technology
- Office of Naval Research
- United States Navy