Major
Marine Biology
Minor(s)
Education
Advisor
Webb, Jacqueline
Advisor Department
Marine Biology
Date
5-2019
Keywords
sei whale, passive acoustic monitoring, phytoplankton
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.
Abstract
The sei whale (Balaenoptera borealis) is an endangered baleen whale species whose distribution and migratory movements are poorly understood. Sei whale populations were decimated by commercial whaling in the 19th and 20th centuries. Much of what is currently known about their distributions comes from historical whaling records. Visual sightings, which may be sporadic and limited by weather and access to remote locations, are the primary source of data for recent research. It is thought that sei whale distributions may be influenced by the distribution of their food, which consists of zooplankton (small crustaceans, like shrimp), small fish, and squid. Phytoplankton, marine algae that are the primary food source for sei whale prey, produce a pigment called chlorophyll-a. Satellites can measure chlorophyll-a concentrations across ocean basins, which can be used as a proxy for distribution of sei whale food resources. Passive acoustic monitoring (listening to sounds in the ocean) provides a method for determining the spatial and temporal distribution of vocalizing animals. Between 2004 and 2015, 283 bottom-mounted acoustic recorders were anchored in the western North Atlantic Ocean from Florida to Greenland, each recording from one month to two years. These recordings were processed with an automated low-frequency sound detection and classification system (LFDCS; Baumgartner & Mussoline 2011) that searched through the recordings and automatically detected sei whale calls based on prior knowledge of their characteristics. These detections were then screened for true acoustic presence of sei whales on all recorders. These acoustic data, along with data on chlorophyll-a concentrations obtained from NASA satellites, were mapped using GIS software. Sei whale distributions along the Eastern seaboard were compared to chlorophyll-a concentrations (as an indicator of the concentration of food resources) throughout each year and among years (2004-2015). These results provide novel insights into sei whale distribution and movements within part of their migratory range and correlate these movements with their food distributions.
Food web and spectrogram of sei whale calls are shown to explain the background and methods of the project.