One of the objectives of the Marine Mammal Protection Act (MMPA) is to ensure species or stocks of marine mammals occurring in waters under the jurisdiction of the United States are neither permitted to diminish beyond the point at which they cease to be a significant functioning element of their ecosystem nor permitted to diminish below their optimum sustainable population optimum sustainable population
With respect to any marine mammal population stock, the number of animals which will result in the maximum productivity of the population or the species, keeping in mind the carrying capacity of the habitat and the health of the ecosystem of which they form a constituent element. [defined under MMPA Section 3(9)]

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. Section 117 of the MMPA provides for the development of stock assessment reports (SARs). SARs are based on the best scientific information available, prepared in consultation with established regional scientific review groups, and include:

  1. A description of the geographic range of the affected stock, including any seasonal or temporal variation in such range

  2. The minimum population estimate, current and maximum net productivity rates, and current population trend, including a description of the information upon which these are based

  3. An estimate of the annual human-caused mortality and serious injury by source and, for a strategic stock strategic stock
    A marine mammal stock (a) for which the level of direct human-caused mortality exceeds the potential biological removal level; (b) which is declining and is likely to be listed under the U.S. Endangered Species Act; or (c) which is listed under the U.S. Endangered Species Act, or is designated as depleted under the MMPA. [defined under MMPA Section 3(19)]

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    , other factors that may be causing a decline or impeding recovery of the stock, including effects on marine mammal habitat and prey

  4. A description of commercial fisheries that interact with the stock, including:

    1. The approximate number of vessels actively participating in each such fishery

    2. The estimated level of incidental mortality and serious injury of the stock by each such fishery on an annual basis

    3. Seasonal or area differences in such incidental mortality or serious injury

    4. The rate, based on the appropriate standard unit of fishing effort, of such incidental mortality and serious injury, and an analysis stating whether such level is insignificant and is approaching a zero mortality and serious injury rate

  5. The status of the stock as one that either: (1) has a level of human-caused mortality and serious injury that is not likely to cause the stock to be reduced below its optimum sustainable population; or (2) is a strategic stock, with a description of the reasons therefor

  6. An estimate of the potential biological removal level potential biological removal level
    The maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population. The potential biological removal level is the product of the following factors: (a) the minimum population estimate of the stock; (b) one-half the maximum theoretical or estimated net productivity rate of the stock at a small population size; and (c) a recovery factor of between 0.1 and 1.0. [defined under MMPA Section 3(20)]

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     for the stock, describing the information used to calculate it, including the recovery factor.

The Service reviews SARs annually for strategic stocks and triennially for non-strategic stocks. If the Service’s review indicates the status of the stock has changed or can be more accurately determined, the Service revises the SAR, which includes a 90-day public comment period.

For information on dolphins, porpoises, whales, seals, and sea lions, contact the National Marine Fisheries Service's Office of Protected Resources.

Documents

West Indian Manatee (Puerto Rico) Stock Assessment Report

On January 23, 2014, the U.S. Fish and Wildlife Service published a Federal Register notice announcing the availability of the final revised marine mammal stock assessment reports for two West Indian manatee stocks: the Florida manatee stock (Trichechus...

West Indian Manatee (Florida) Stock Assessment Report

On January 23, 2014, the U.S. Fish and Wildlife Service published a Federal Register notice announcing the availability of the final revised marine mammal stock assessment reports for two West Indian manatee stocks: the Florida manatee stock (Trichechus...

Southern Sea Otter Stock Assessment Report

On June 24, 2021, the U.S. Fish and Wildlife Service published a Federal Register notice announcing the availability of the final revised marine mammal stock assessment report for the southern sea otter (Enhydra lutris nereis) stock.

Polar Bear (Southern Beaufort Sea) Stock Assessment Report

On June 24, 2021, the U.S. Fish and Wildlife Service published a Federal Register notice informing the public that we have finalized revised marine mammal stock assessment reports for each of the two polar bear (Ursus maritimus) stocks in Alaska: The...

Polar Bear (Chukchi Bering Sea) Stock Assessment Report

On June 24, 2021, the U.S. Fish and Wildlife Service published a Federal Register notice informing the public that we have finalized revised marine mammal stock assessment reports for each of the two polar bear (Ursus maritimus) stocks in Alaska: The...

Pacific Walrus Stock Assessment Report

On April 1, 2014, the U.S. Fish and Wildlife Service published a Federal Register notice announcing the availability of the final revised marine mammal stock assessment report for the Pacific walrus (Odobenus rosmarus divergens) stock in Alaska.

Northern Sea Otter (Southwest Alaska) Stock Assessment Report

On April 21, 2014, the U.S. Fish and Wildlife Service published a Federal Register notice informing the public that we have finalized revised marine mammal stock assessment reports for each of the three northern sea otter (Enhydra lutris kenyoni) stocks...

Northern Sea Otter (Washington) Stock Assessment Report

On April 22, 2019, the U.S. Fish and Wildlife Service published a Federal Register notice announcing the availability of the final revised marine mammal stock assessment report for the northern sea otter (Enhydra lutris kenyoni) stock in the State of...

Northern Sea Otter (Southeast Alaska) Stock Assessment Report

On April 21, 2014, the U.S. Fish and Wildlife Service published a Federal Register notice informing the public that we have finalized revised marine mammal stock assessment reports for each of the three northern sea otter (Enhydra lutris kenyoni) stocks...

Northern Sea Otter (Southcentral Alaska) Stock Assessment Report

On April 21, 2014, the U.S. Fish and Wildlife Service published a Federal Register notice informing the public that we have finalized revised marine mammal stock assessment reports for each of the three northern sea otter (Enhydra lutris kenyoni) stocks in...

Species

Programs

The Ecological Services Program works to restore and protect healthy populations of fish, wildlife, and plants and the environments upon which they depend. Using the best available science, we work with federal, state, Tribal, local, and non-profit stakeholders, as well as private land owners, to...
We provide leadership in the conservation and management of our nation's marine mammals under our jurisdiction – sea otters, Pacific walruses, polar bears, and West Indian manatees – as well as the marine ecosystems that support them.

Library Collections

One of the goals of the Marine Mammal Protection Act (MMPA) is to ensure that stocks of marine mammals occurring in waters under the jurisdiction of the United States do not have a level of human-caused mortality and serious injury that is likely to cause the stock to be reduced below its optimum...