Marine Mammal Research Surveys in NOAA’s Southeast Region
How survey data is collected and used to inform marine mammal population assessments in the Southeast.
Our marine mammal scientists produce data, information, and scientific advice that serves as a foundation of knowledge upon which living marine resource managers in the southeastern United States depend. Before we can successfully manage or conserve any species, we first have to know more about them.
Our primary way of doing this is through population assessments. During these research surveys we collect and analyze data to understand the geographic range, size, and trends of marine mammal populations. We also collect data on their habitat to assess which environmental parameters may be influencing their distribution.
These surveys are the main source of data used to develop Stock Assessment Reports, which are mandated by the Marine Mammal Protection Act (MMPA). These assessments also give us a better picture of population trends over many years. It also helps to have this information in case there is an acute event — such as harmful algal blooms or oil spills — or to study distribution shifts and trends resulting from potential effects of climate change.
At NOAA’s Southeast Fisheries Science Center, we work with many partners and focus on dolphin and whale populations in our region. This includes bay, estuarine, and coastal waters, deeper waters on the continental shelf (from approximately 3 nautical miles from shore to 200meters/656feet water depth), and oceanic (waters deeper than 200meters/656feet) waters of the Atlantic, Gulf of Mexico, and Caribbean in the United States.
While different surveys are designed to address different research questions and may focus on a particular species or habitat, they all rely on locating and observing the animals.
Our research surveys rely on aircraft and ships operated by NOAA’s Office of Marine and Aviation Operations. In the Southeast region, we primarily rely on three NOAA ships, Oregon II, Pisces and Gordon Gunter, for surveys in offshore waters. It takes about 35 people to staff a research expedition — 10 to 15 scientists plus the NOAA Corps officers and civilian professional mariners who operate the ship.
In the shallower waters of the continental shelf, we often collect data from above. Our teams use NOAA’s Twin Otter, a versatile aircraft that carries two pilots and up to six scientists, to collect data primarily on marine mammals (whales and dolphins) and sea turtles. We also conduct near-shore surveys using small vessels, particularly to study bottlenose dolphins.
How We Conduct Surveys
During these surveys, the vessels and aircraft follow pre-established tracklines within a specific area, like mowing your lawn. Scientifically, this type of research is known as line-transect survey. As we do that, we record all sightings of marine mammals — listing the number of animals and species we see. During aerial surveys, in addition to dolphins and whales, we also record sea turtles as well as some fish species, like whale sharks and giant manta rays, if we see them.
Our projects are often collaborations between multiple agencies. For example, since 2010, we have partnered with NOAA’s Northeast Fisheries Science Center to conduct surveys under the Atlantic Marine Assessment Program for Protected Species (AMAPPS). This program is funded by the Bureau of Ocean Energy Management (BOEM) and the U.S. Navy. In 2017, together with other federal agencies, we developed a similar monitoring program for the U.S. waters of the Gulf of Mexico under the Gulf of Mexico Marine Assessment Program for Protected Species (GoMMAPPS) also funded by BOEM.
On vessel surveys, we collect in-situ environmental data as well, like sea surface salinity and temperature. We use a CTD device to measure water conductivity (C), temperature (T), and depth (D). We also use a scientific echosounder (similar to a "fish finder") to measure the quantity and type of prey present in the water column. All these measurements help us determine and understand the environment that marine mammals and sea turtles depend upon.
During vessel surveys, we also tow a hydrophone array behind the ship to listen for sounds produced by whales and dolphins. Since some species of marine mammals like beaked and sperm whales spend a considerable amount of time underwater and therefore are hidden from view, it can be difficult to see them from the vessel. That’s when the acoustic component of our survey comes into play, as the hydrophone "listens" to the unique sound produced by these animals, complementing the visual aspect of our surveys.
What We Have Learned
The main goal of our line-transect surveys is to assess the distribution and abundance of marine mammals and sea turtles. This provides managers the best available data for the protection of these species through the Stock Assessment Reports.
Marine mammal and sea turtle sighting data are also combined with remotely sensed data from satellites to understand the oceanographic drivers of species distribution. For example, the AMAPPS Marine Mammal Model Viewer displays the density of several marine mammal species by season for the U.S. East Coast.
Through the AMAPPS and GoMMAPPS programs between 2010 and 2020 we have conducted 6 ship-based and 17 aerial surveys that combined covered more than 187,000 km (more than 100,000 nautical miles, that is enough to go around the Earth 4.5 times along the Equator).These surveys recorded more than 5,600 marine mammal sightings, including over 70,000 animals.
Data from these surveys help us manage and understand the distribution of marine mammal populations in the western North Atlantic and the U.S. Gulf of Mexico. While there are some species differences between them, both ocean basins share a lot of commonly seen species, such as: common bottlenose, pantropical spotted and Atlantic spotted dolphins and sperm whales. You can find more information about the marine mammal species that occur in U.S. waters at the NOAA Fisheries Marine Mammals Directory.
Data collected by the Southeast Fisheries Science Center are being archived at the National Centers for Environmental Information and can be accessed via the NCEI Geoportal. In addition, some of the data we’ve collected over the decades can be accessed on the OBIS-Seamap platform.