Passive Acoustic Research at the Southeast Fisheries Science Center

The Passive Acoustic Ecology Program conducts research projects that use passive acoustics to assess populations and improve our understanding of cetaceans in the Gulf of America (formerly Gulf of Mexico) and U.S. waters of the Western Atlantic.

Southeast

Two false killer whales jumping through blue, open ocean water — False killer whales (Pseudorca crassidens) in the Gulf of America. Credit: NOAA Fisheries (Permit #14450)

Marine Assessment Programs for Protected Species Surveys

As part of our marine mammal population assessment research, Southeast Fisheries Science Center scientists conduct Marine Assessment Programs for Protected Species projects in the Atlantic, and Gulf of America. Our team of acoustic scientists use custom towed hydrophone arrays and specialized computer software to listen to and record the sounds that whales and dolphins (cetaceans) produce underwater.

Detecting these sounds is important for assessing the distribution and abundance of marine mammals. This is particularly important for cryptic species that are difficult to see or identify, such as pygmy or dwarf sperm whales and multiple species of beaked whales. Our scientists use these data to estimate the abundance of deep-diving sperm whales and beaked whales. Recordings of dolphins, with associated visual species identification, are used to develop acoustic species classification tools. These tools help us to identify species from just their sounds and to better understand how species’ sounds may differ across locations.

This visual representation shows how sound frequency (y-axis) changes over time (x-axis), with sound loudness represented by color. — Spectrogram of dolphin echolocation clicks and whistles recorded on a towed array during the Gulf of Mexico Marine Assessment Program for Protected Species surveys. This visual representation shows how sound frequency (y-axis) changes over time (x-axis), with sound intensity represented by color. Credit: NOAA Fisheries

Mapping the change in bearing from the vessel location to the acoustic detections as the ship continues. — Mapping the change in bearing from the vessel location to the acoustic detections as the ship continues on a trackline allows scientists to triangulate and localize the animals producing sounds. In this example, three individual animals were detected and localized. Using a linear-array, scientists aren’t able to determine whether animals occurred to the left or right of the trackline, but new 3D array technologies are being developed to improve this. Credit: NOAA Fisheries/ Kat Ternus

LISTEN GoMex

Long-term Investigations into Soundscapes, Trends, Ecology, and Noise in the Gulf of Mexico

Our ship-based surveys in the Gulf of America provide broad-scale but infrequent visual and acoustic data. To complement these data, we are expanding our passive acoustic monitoring program to collect high-temporal resolution data at fixed acoustic mooring locations throughout the Gulf.

In 2020, Southeast Center scientists, along with Scripps Institution of Oceanography and other partners, began deploying a network of HARPs (High-frequency Acoustic Recording Packages) to record marine mammal sounds and ocean soundscapes in U.S. and Mexican waters. These efforts are supported by the RESTORE Science Program and Deepwater Horizon Open Ocean Restoration noise impact reduction project. The 5-year LISTEN GoMex project will characterize seasonal, annual, and decadal trends in marine mammal species occurrence and density in the Gulf of America. It will also assess the role of ocean conditions and human activities in driving these trends.

Additionally, the project will characterize human-made sound sources, such as seismic airguns, small and large vessels, and explosives, that impact the Gulf environment. This research supports restoration activities to recover whales and dolphins harmed by the 2010 Deepwater Horizon oil spill. The Deepwater Horizon noise impact reduction restoration project will use the data collected to understand how noise varies throughout marine mammal habitat to develop projects aimed at decreasing human noise impacts on marine mammals.

This map of the Gulf of America includes our long-term passive acoustic recording sites. — Gulf of America long-term passive acoustic recording sites for the five-year LISTEN GoMex project. There are eight long-term sites for monitoring longer term trends (dark blue circles), 20 short-term 1-year sites for broad spatial coverage (circles color coded by deployment year), and two sites for collecting data from human-made noise sources (white circles). Credit: NOAA Fisheries/Melissa Soldevilla

Rice’s Whale Acoustic Behavior and Distribution

Rice’s whales are one of the most endangered whale species in the world, with a population estimated at fewer than 100 individuals. Very little is known about these whales. We are conducting a suite of research projects to learn more about their ecology and to help managers develop management and conservation strategies.

We are investigating the whale’s call repertoire and behavior to learn what sounds they produce and how they use them. This foundational information is needed to use passive acoustic methods to study the whales. Additionally, our acousticians are conducting studies to understand when and where Rice's whales are found within their core habitat in the northeastern Gulf of America and whether they occur more broadly throughout the Gulf.

This information will help us understand where and when Rice’s whales overlap with human-caused threats so that managers can develop effective mitigation strategies to improve their recovery.

Learn about Rice’s whales—their population status, habitat, threats, and other frequently asked questions.

Rice's whale from above. — Rice’s whale (Balaenoptera ricei). Credit: NOAA Fisheries (MMPA Permit #21938)

The Underwater Soundscape of the Gulf of America

The Gulf of America is one of the noisiest bodies of water in the United States. Low-frequency noise from seismic airgun surveys for oil and gas exploration and from shipping traffic are the main contributors to high noise levels in the Gulf. In addition to marine mammal calls, our passive acoustic recorders record other sounds from the environment. These include wind and waves, sounds produced by other animals, and sounds produced by human activities.

We are working to characterize the natural and human-made noise sources that contribute to the Gulf of America soundscape. We deploy calibrated HARPs in the northern Gulf of America as part of our Rice’s whale monitoring and LISTEN GoMex projects. The results of these studies will help us understand noise levels and noise sources in Rice’s whale habitats. They will also provide information to help reduce impacts of human-made noise on marine mammals under the Deepwater Horizon oil spill restoration project.

Spectrogram of seismic airgun pulses from the Gulf of Mexico. — Spectrogram of seismic airgun pulses from moored recorders from the Gulf of America. This visual representation shows how sound frequency (y-axis) changes over time (x-axis), with sound intensity represented by color (cool = low, warm = high). Credit: NOAA Fisheries/Amanda Debich

Link to audio file of seismic airgun pulses from the Gulf of America (mp3)

North Atlantic Right Whale Calving Grounds and Migration Corridors

a North Atlantic right whale and it's baby during calving swimming in ocean along the surface. — North Atlantic right whale mother and calf. Credit: Clearwater Marine Aquarium Research Institute (NOAA permit #20556-01)

Southeast Center researchers use moored passive acoustic instruments to learn how North Atlantic right whales use their calving habitat in southeastern U.S. waters. In collaboration with the Northeast Fisheries Science Center, we also learn the extent of their migratory corridor between the southeastern calving grounds and northeastern feeding grounds.

Southeast Center scientists have been deploying passive acoustic moorings in the calving habitat since 2003, and throughout the migratory corridor since 2015. These data provide information on when and where North Atlantic right whales are during this important life stage. This knowledge can be used to reduce risks of vessel collisions and fisheries entanglements, two major causes of death for these endangered whales.

More Information

Passive Acoustic Monitoring in the Southeast United States

Passive Acoustic Technologies Used at the Southeast Fisheries Science Center

Listening to a New Species, the Rice's Whale, to Support its Conservation

Deploying Passive Acoustic Recorders for North Atlantic Right Whale Calving Season

Marine Mammal and Turtle Division

Southeast Fisheries Science Center

Last updated by Southeast Fisheries Science Center on 04/24/2025