Leopard seal hauled out on the ice.

Marine Mammal Protection


Science is critical to understanding the needs and status of marine mammal populations, as well as the threats to their health and well-being. NOAA Fisheries pursues a scientific understanding of these topics because it is essential to conservation efforts. Examples of our work include assessing and monitoring marine mammal stocks, researching disease agents (e.g., pathogens, parasites, and harmful algal blooms), and developing gear modifications to reduce entanglement and bycatch.

Stock Assessments

The Marine Mammal Protection Act defines a marine mammal stock as a group of individuals “of the same species or smaller taxa in a common spatial arrangement that interbreed when mature.” Assessing stocks gives us valuable information on marine mammal population trends, productivity rates, estimates of human-caused mortality and other sources of serious injury, and more. It allows us to evaluate the effectiveness of conservation and recovery measures, and to adjust management approaches as needed.

Stock assessment reports for all marine mammals in U.S. waters were first required when the MMPA was amended in 1994. Since that time, all stocks have been reviewed at least every three years or as new information becomes available. Stocks that are designated as strategic  are reviewed annually. Each draft stock assessment report is peer-reviewed by one of three regional Scientific Review Groups and revised and published after a public comment period.

Data collection, analysis, and interpretation are conducted through marine mammal research programs at each of our Fisheries Science Centers and by other researchers.

Learn more about marine mammal stock assessments

Find the most recent stock assessment reports

Field Surveys

Ship-based and aerial surveys are critical to achieving our marine mammal population assessment goals, which include estimating abundance and examining trends and human impacts relative to management objectives. Our science centers conduct and manage a limited number of marine mammal surveys each year, often with external collaborators. The number of surveys depends on funding and available ship time and flight time.

Learn more about our surveys

Ocean Acoustics

The efficiency of sound travel under water has led to increasing concern over how man-made sound potentially impacts the underwater environment. Our scientists support and conduct research to examine these potential impacts on marine animals and to increase understanding of:

  • How marine animals use sound.

  • How underwater acoustics can be used to assess marine animal populations.

  • How and to what degree anthropogenic activities are changing the underwater soundscape.

  • How these changes may potentially impact marine animals in their acoustic habitat.

  • What measures can be taken to mitigate potential impacts.

Learn more about ocean acoustics

Climate and Ecosystem Science

Understanding climate change impacts on living marine resource distribution and occurrence patterns is a high priority for NOAA Fisheries. We know relatively little about the effects of global and regional climate dynamics on species distribution, abundance, and prey availability. The Arctic in particular is a window to changing climate patterns and a suitable biological laboratory to observe and record the impacts of receding sea ice, warming sea surface temperatures, and variable energy flow. These impacts all affect key marine ecosystem functions and native tribal communities that depend on Arctic resources for their livelihood and sustenance.

Learn more about climate-related changes in ocean ecosystems

Bycatch Reduction

Reducing bycatch of protected species can improve the recovery of marine mammals. Together with the fishing industry, we work to minimize bycatch by developing technological solutions and changes in fishing practices. These include gear modifications, avoidance programs, and/or improved fishing practices in commercial and recreational fisheries.

Learn more about the Bycatch Reduction Engineering Program

Marine Mammal Health and Strandings

Marine mammal health is a key indicator of the overall health of our oceans. We and our stranding network partners perform vital research into causes of death and emerging diseases in marine mammals. This enables biologists to monitor the health of species populations and identify threats. They perform necropsies on freshly dead animals whenever possible. Blood serum, blubber, and tissue tests can provide information on contaminant loads and pathogens. During examinations, biologists also look for clues such as evidence of blunt force trauma (which can be an indicator of ship strikes) or signs of entanglement and fishery interactions. Data from stranding events are collected in a national database, and the information is used to increase our understanding of marine mammal communities and to monitor the health of their populations.

Learn more about the Marine Mammal Health and Stranding Response Program

Photo-Identification Surveys

Marine mammals can often be identified by markings such as blemishes, fin nicks and notches, and scars. Several research programs rely on these markings—visible in images obtained during photo-identification surveys—to distinguish and catalog individual animals.

Learn more about the FinBase photo-identification database system

Economics Research

Species valuation studies enable us to assess the national benefits derived from protected species including marine mammals such as whales, porposies, and sea lions. Protecting a species through laws and policies implies that society considers these species to be valuable. Economics can be used to assess the value that people have for preserving a species for future generations regardless of whether they ever view the species or not.

Learn more about protected species economics research

Advanced Technologies

Learn about other advanced technologies used by our scientists—including drones, satellite tagging and tracking, and genetic research—to study marine mammals and other ocean animals.