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NOAA Fisheries
Office of Protected Resources
Acropora palmata thicket on Mona Island, Puerto Rico. Andy Bruckner, 1996Coho salmon painting, Canadian Dept of Fisheries and OceansMonk seal, C.E. BowlbyHumpback whale, Dr. Lou Herman
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Conservation, Protection, & Recovery
Species of Concern
Listing of Species
Recovery of Species
Marine Mammal Conservation Plans
Cooperation with States
Grants to Tribes
Interagency Consultation
   Biological Opinions

Human Impacts
Fisheries Interactions (bycatch)
Ocean Sound/Acoustics
Ship Strikes
Viewing Wildlife

International Cooperation

Marine Mammal Health & Stranding
Marine Mammal National Database
National Tissue Bank
Prescott Grants
Unusual Mortality Events
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OPR Site Map

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FAQs: Whale, Dolphin, Seal, and Sea Lion (Marine Mammal) Strandings

Why do marine mammals strand?
In most stranding cases, the cause of stranding is unknown, but some identified causes include:

  • disease
  • parasite infestation
  • harmful algal blooms
  • injuries due to ship strikes
  • fishery entanglements
  • pollution exposure
  • trauma
  • starvation

In addition, strandings often occur after unusual weather or oceanographic events.

In the past few years, increased efforts in examining carcasses and live stranded animals has increased our knowledge of mortality rates and causes, allowing us to better understand population threats and pressures.

What information is gained from necropsies of stranded marine mammals?
If a stranded marine mammal has recently died, then a significant amount of valuable information can be gained from it. For instance:

  • complete pathology to investigate diseases and parasites
  • reproductive biology data
  • life history (what does the animal eat, how long do they live, how many calves do they have, how old are they when they first reproduce)
  • pollution
  • normal biology and physiology parameters

These types of sampling opportunities also help validate and increase understanding and interpretation of data collected from wild populations.

Through necropsies we have learned a significant amount about the basic physiology and biology of animals that are not accessible in the wild or through any other means.

Necropsies have also provided data on the incidence of human interactions including:

  • ship strikes
  • entanglements
  • hooks
  • marine debris ingestions

These data help us to make better management decisions about these stocks of marine mammals.

How many marine mammal strandings occur?
Over the 9-year period from 2001-2009:

Region Cetacean Strandings Pinniped Strandings Total
Marine Mammal Strandings
Northeast 3,663 7,873 11,536
Southeast 5,872 98 5,970
Southwest 1,591 25,308 26,899
Northwest 588 5,193 5,781
Alaska 673 556 1,229
Pacific Islands 158 76 234
U.S. Totals 12,545 39,104 51,649

How many marine mammal rehabilitation facilities are there in the United States?
There are currently 32 facilities that can rehabilitate stranded marine mammals under NMFS jurisdiction. In all, there are over 120 organizations or stranding network participants authorized by NMFS to respond to marine mammal strandings, but only some of those facilities can rehabilitate marine mammals.

There are many organizations/stranding network participants who are strictly first responders on the beach (i.e., they rescue the animal, but don't have adequate facilities to rehabilitate marine mammals).

Some network participants respond only to dead marine mammal strandings. Responders to dead strandings make up the vast majority of responders and may include Federal, state, and local governmental entities, non-profit organizations, academic institutions, museums, scientists, and managers among others.

NMFS oversees marine mammal stranding response through a Regional Stranding Coordinator in all 6 of NMFS' regions.

What is the scope of the Marine Mammal Health and Stranding Response Program?
Marine mammal stranding networks in the United States make up one facet of a broader, more comprehensive program called the Marine Mammal Health and Stranding Response Program (MMHSRP), established in the late 1980s in response to growing concern about marine mammals washing ashore in U.S. waters. The MMHSRP's goals are to:

  • facilitate collection and dissemination of data
  • assess health trends in marine mammals
  • correlate health with available data on physical, chemical, environmental, and biological parameters
  • coordinate effective responses to unusual mortality events

This program was formalized by the 1992 Amendments to the Marine Mammal Protection Act, and the National Marine Fisheries Service (NMFS) was designated as the lead agency to coordinate related activities. The program has the following components:

  • Stranding networks
    To respond to marine mammal strandings, volunteer stranding networks were established in all coastal states and are authorized through Stranding Agreements from the NMFS regional offices. Through a National Coordinator and 6 regional coordinators, NMFS oversees, coordinates, and authorizes these activities and provides training to personnel.

  • Biomonitoring
    In recent years, high concentrations of potentially toxic substances in marine mammals and an increase in new diseases have been documented, and scientists have begun to consider the possibility of a link between these toxic substances and marine mammal mortality events. These studies contribute to a growing, worldwide effort of marine mammal biomonitoring not only to help assess the health and contaminant loads of marine mammals, but also to assist in determining anthropogenic impacts on marine mammals, marine food chains and marine ecosystem health. NMFS provides participants in the program with training and some financial support. Using strandings and bycatch animals, the participants provide tissue/ serum archiving, samples for analyses, disease monitoring and reporting and additional response during disease investigations.

  • Analytical Quality Assurance (AQA)
    This aspect of the MMHSRP was designed to ensure accuracy, precision, level of detection, and intercomparability of data in the chemical analyses of marine mammal tissue samples. The AQA consists of annual interlaboratory comparisons and the development of control materials and standard reference materials for marine mammal tissues. The NIST Charleston facility is the lead for this activity.

  • Response to Unusual Mortality Events
    In response to the 1987-88 dolphin die-off, NMFS established a Working Group on Marine Mammal Unusual Mortality Events to create criteria for determining when an unusual mortality event is occurring and then to direct responses to such events. The Working Group is periodically called upon to lend its expertise in situations where circumstances indicate an unusual mortality event may be occurring and may provide guidance throughout the event.

  • John H. Prescott Marine Mammal Rescue Assistance Grant Program
    Through the John H. Prescott Marine Mammal Rescue Assistance Grant Program (Prescott Grant Program), NMFS funds eligible members of the National Marine Mammal Stranding Network through grants and cooperative agreements. Funds are used for the recovery or treatment of marine mammals; the collection of data from living or dead stranded marine mammals for health research; and facility operation costs.

  • National Marine Mammal Tissue Bank
    The National Marine Mammal Tissue Bank was formally established in 1992 and provides protocols and techniques for the long-term storage of tissues from marine mammals for retrospective contaminant analyses. The Tissue Bank is maintained by NIST as part of the National Biomonitoring Specimen Bank and the Marine Environmental Specimen Bank, which was established in 2002. The Tissue Bank uses the biomonitoring sites noted above and other trained personnel to collect tissues on specific indicator species (e.g., Atlantic bottlenose dolphins, Atlantic white-sided dolphins, pilot whales, harbor porpoise, etc.), mass stranding animals, and mortality events.


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