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Marine Mammal Stock Assessments

Assessing marine mammal stocks gives us valuable information on population trends, productivity rates, estimates of human-caused mortality and other sources of serious injury, and more. These assessments allow us to evaluate the effectiveness of conservation and recovery measures, and to adjust management approaches as needed.

The two Arpeggios swimming Right whale (Eubalaena glacialis) Arpeggio, also known as egno 2753, was born in 1997 (her mother is egno 1153).

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.” 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 science centers and by other researchers.

The U.S. Fish and Wildlife Service prepares SARs for marine mammals under their jurisdiction including polar bears, sea otters, walruses, and manatees.

Information Contained in Stock Assessment Reports

Each report includes:

How the Reports Are Developed

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

The MMPA provides broad narrative descriptions of what has to be included in stock assessment reports. For example, the reports require a "minimum population estimate" which means we have "reasonable" assurance there are at least the estimated number in the population.

Guidelines for Assessing Marine Mammal Stocks

To include values for the required elements in the reports, NOAA Fisheries had to translate qualitative concepts into quantitative terms. After building a scientific foundation through simulation modeling, NOAA Fisheries convened a workshop in La Jolla, California, in 1994 to prepare guidelines for selecting specific values to include in the reports.

Using a process similar to reviewing the stock assessment reports (i.e., NOAA Fisheries discussion and products, review by Scientific Review Groups, and public review and comment), we periodically revise the guidelines to ensure a nationally consistent approach.

Learn more about the guidelines for assessing marine mammal stocks

How the Information Is Used

The information contained in stock assessment reports is used to:

  • Identify and evaluate the status of marine mammal populations and the effects of human activities upon them.

  • Authorize the "taking" of marine mammals incidental to human activities.

  • Design and conduct appropriate conservation measures.

  • Evaluate the progress of each fishery in reducing its incidental mortality and serious injury to insignificant levels approaching a zero mortality and serious injury rate.

Learn More

Do NOAA Fisheries and the U.S. Fish and Wildlife Service prepare reports for all populations of marine mammals worldwide?

No. We prepare reports only for marine mammal stocks that occur in waters under U.S. jurisdiction, as stated in the MMPA.

How many marine mammal stock assessment reports are reviewed or prepared annually?

All stocks are reviewed at least every three years or as new information becomes available. Stocks that are designated as "strategic" are reviewed annually.

The first stock assessment reports prepared in 1995 included about 165 reports on marine mammal stocks in U.S. waters:

  • Approximately 60 reports in the Atlantic Ocean and Gulf of Mexico.

  • Approximately 60 reports along the Pacific Coast of the continental United States and Hawaii.

  • Approximately 35 reports in Alaska and the North Pacific.

  • Approximately 10 reports for polar bears, sea otters, walrus, and manatees in U.S. waters (prepared by the U.S. Fish and Wildlife Service).

The number of reports may vary from year to year because stock identification is subject to change, and marine mammal stocks may be added or removed from the list of compiled reports due to changes in distribution.



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Pod of killer whales.

Last updated by Office of Protected Resources on February 06, 2024