Marine Mammal Stock Assessments
NMFS prepares annually marine mammal stock assessment reports (SARs). The reports are prepared in consultation with one or more of three regional Scientific Review Groups (SRGs) and are also available for public review and comment. The U.S. Fish and Wildlife Service (FWS) also prepares SARs for marine mammals under their jurisdiction (manatees, polar bears, sea otters, and walruses).
NMFS reviews reports for "strategic stocks" of marine mammals annually. For non-strategic stocks, reports are reviewed every three years, or when new information becomes available. If the reviews show that the status of the stock has changed or can be assessed more accurately, NMFS revises the report in consultation with the SRGs and after public review and comment.
NMFS completed its first SARs in 1995 and has revised them, as needed, annually since then. In general, NMFS updates SARs regularly to incorporate new information as available--not only when a change in status occurs or can be determined with greater accuracy.
Does NMFS/FWS 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.
What information can I find in a stock assessment report?
Each report includes:
- a description of the stock's geographic range
- a "minimum population estimate"
- current population trends
- current and maximum net productivity rates
- "Potential Biological Removal" levels
- status of the stock
- estimates of annual human-caused mortality and serious injury by source
- descriptions of other factors that may be causing a decline or impeding the recovery of"strategic stocks"
How does NMFS acquire the information to include in stock assessment reports?
Data collection, analysis, and interpretation are conducted through marine mammal research programs at each of NMFS' Fisheries Science Centers and by other researchers.
The MMPA provides only broad narrative descriptions of the kinds of information that 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.
To include values for the required elements in the reports, NMFS had to translate these qualitative concepts into quantitative terms. After building a scientific foundation through simulation modeling, NMFS convened a workshop in La Jolla, CA, in 1994 to prepare guidelines for selecting specific values to include in the reports. Using a process similar to reviewing the stock assessment reports (NMFS discussion and products, review by Scientific Review Groups, and public review and comment), these guidelines have been revised two times since they were completed with the initial stock assessment reports in 1995.
More information on the guidelines is available.
How is the information used?
This information 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
How many marine mammal stock assessment reports are reviewed or prepared annually?
The first stock assessment reports, in 1994, included (with USFWS) about 165 reports on marine mammal stocks in U.S. waters, including:
- ~60 reports in the Atlantic Ocean and Gulf of Mexico
- ~60 reports along the Pacific Coast of the continental United States and Hawaii
- ~35 reports in Alaska and the North Pacific
- ~10 reports for manatees, polar bears, sea otters, and walrus in U.S. waters (prepared by FWS)
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.
- NMFS. 2004. A Requirements Plan for Improving the Understanding of the Status of U.S. Protected Marine Species [pdf] [6.1 MB]. Report of the NOAA Fisheries National Task Force for Improving Marine Mammal and Turtle Stock Assessments. U.S. Dep. Commerce, NOAA Tech. Memo. NMFS-F/SPO-63, 112 p.
Updated: August 19, 2015