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FAQs on the California Sea Lion UME in California

NOAA Fisheries has declared an Unusual Mortality Event due to significant numbers of California sea lion strandings (in five counties) beginning in January 2013.

Q: What is an Unusual Mortality Event?

A: An Unusual Mortality Event (UME) is defined under the Marine Mammal Protection Act as a stranding event that is unexpected, involves a significant die-off of any marine mammal population, and demands immediate response. There are seven criteria used to determine whether a mortality event is "unusual." If the Working Group on Marine Mammal Unusual Mortality Events (Working Group), a group of marine mammal health experts, determines that an event meets one or more of the criteria, then an official Unusual Mortality Event is declared.

Q: What is the risk to humans?

A: Sea lions are wild animals and may bite people if approached closely. Because marine mammals and people can share diseases, the California Department of Public Health is urging the general public to stay away from marine mammals (either live or dead marine mammals) that are stranded on the beach. It is not clear at this time if there is any infectious disease risk to human health through contact with these animals.

Q: What criteria have been met?

A: The Working Group concluded that at least one of the seven criteria established for designation of a UME has been met. These mortalities are unusual because there is a marked increase in the magnitude or a marked change in the nature of morbidity, mortality or strandings when compared with prior records.

Q: How widespread is this Unusual Mortality Event?

A: Increased strandings of California sea lions have occurred in the following counties: Santa Barbara, Ventura, Los Angeles, Orange, and San Diego. 

Q: When did the first reports of increased strandings of sea lions come in?

A: In January 2013, the California Marine Mammal Stranding Network started to notice an increase in California sea lions strandings in the region.  

Q: What are the findings in stranded animals?

A: At this time, the UME seems confined to California sea lion pups (born summer 2012). All live animals are currently being rescued and taken to rehabilitation centers. Consistent findings in the pups are emaciation and dehydration with most animals very underweight for their age.

Q: Have other marine mammals been affected by this die-off event?

A: No, stranding rates for other pinniped species have been normal for this time of year and no increase has been observed in cetacean strandings. The network will continue to monitor strandings in all species of marine mammals in the area and communicate with the wildlife rehabilitation facilities regarding changes in sea bird admissions.

Q: What is the current California sea lion population and where are the main rookeries?

A: The most recent Stock Assessment Report for California sea lions was issued in 2011. The current estimated total population size is 296,750 animals, with an annual increase of 5.4%. The main US rookeries are located on the Channel Islands.

Q: What are the next steps in the investigation now that an Unusual Mortality Event has been declared?

A: As part of the UME investigation process, an independent team of scientists (investigation team) is being assembled to coordinate with the Working Group to review the data collected and to determine potential next steps. The group will focus on the immediate response and develop the investigative plan. The response may continue over several months and the investigation may require months, or even years of data collection, analysis, and interpretation.

Q: What additional resources are now available to pursue the investigation, since an Unusual Mortality Event has been declared?

A: A UME declaration provides additional expertise from the Working Group (an international and multi-disciplinary team of scientists), additional partners, and access to additional funding through the National Contingency Fund. In addition this will provide a detailed investigative plan for the investigation that may include more targeted necropsies; further testing of samples for biotoxins, bacterial or viral agents; and diagnostic pathology services. Finally, this process will provide national and international scientific review of findings and interpretations.

Q: Will you be collecting additional biological and environmental information?

A: The Stranding Network will continue to collect and analyze samples as needed to evaluate the situation. The Working Group will decide whether additional information is needed.

Q: When will you have some results to share?

A: The investigative team is in process of developing an investigative plan to test samples from both live and dead animals. Blood and tissues samples will be tested for bacterial, viral and other infectious agents. Samples will also be tested for radio-nucleotides. Results will be available in 1-3 months, and you can track the progress of our investigation from our California Sea Lion UME website.

Q: Have there been any specific instances of humans contracting a disease from the sea lions?

A: To date, no cases of human illness have been reported from this current event.

Q: Are there any risks to pets?

A: Pets should always be kept away from marine mammals, particularly diseased or dead marine mammals.

Q: How many sea lion Unusual Mortality Events have previously occurred in California?

A: This is the sixth UME involving California sea lions that has occurred in California. Prior UMEs were declared in 1991, 1992, 1998, 2000 and 2002. Previous UMEs were caused by leptospirosis (1991), El Niño conditions (1992) and domoic acid toxicity (1998, 2000, 2002). To date, 57 UMEs have been formally declared in U.S. waters since 1991 (including the current UME).

Q: How many marine Unusual Mortality Events have previously occurred along the West Coast of the United States?

A: This is the 17th UME to occur along the West Coast of the U.S. All previous events involved either California sea lions, harbor seals, Guadalupe fur seals, harbor porpoises, common dolphins, gray whales, other species of cetaceans (whales and dolphins), and/or sea otters. To date, 57 UME have been formally declared in U.S. waters since 1991 (including the current UME).

Q: Where can I find additional information on California sea lions and other Unusual Mortality Events?

A: You can find more information on our website:

Q: What should people do if they encounter a sick sea lion on the beach?

A: Please contact your local stranding network or local authorities to report a live or dead stranded sea lion.

Q: What should people do if they witness harassment of a sea lion on the beach?

A: To report violations or for more information on NOAA’s Office of Law Enforcement call the toll-free number: 1-800-853-1964.

Q: What is the link, if any, of these marine mammal illness/deaths to seafood safety?

A: State and Federal Agencies continue to conduct routine testing of seafood for consumer safety while NOAA Fisheries is working with a group of wildlife researchers to test for a wide range of possible disease factors causing this California sea lion UME. No link has been established at this time between these sea lion strandings and any potential seafood safety issues.

Updated: March 23, 2015