Marine Mammal Unusual Mortality Events

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Background
An unusual mortality event (UME) is defined under the Marine Mammal Protection Act as "a stranding that is unexpected; involves a significant die-off of any marine mammal population; and demands immediate response." In recent years, increased efforts to examine carcasses and live stranded animals have improved the knowledge of mortality rates and causes, allowing a better understanding of population threats and stressors and the ability to determine when a situation is "unusual." Understanding and investigating marine mammal UMEs is important because they can serve as indicators of ocean health, giving insight into larger environmental issues which may also have implications for human health and welfare.

The marine mammal UME program was established in 1991. From 1991 to the present, there have been 41 formally recognized UMEs in the U.S involving either single or multiple species and dozens to hundreds of individual marine mammals per event. The table below indicates the years, species, and cause (determined or suspected) for each UME. UMEs have occurred in and along the Atlantic, Gulf of Mexico, and Pacific coasts of the U.S., as well as Alaska and Hawaii. California and Florida are the states with the most declared UMEs. Bottlenose dolphins have been the most common species involved in UMEs, followed by California sea lions and manatees.

Causes have been determined for 23 of the 41 UMEs documented since 1991. UME causes have included infections, biotoxins (poisonous substances produced by a living organism), human interactions, and malnutrition. Since 1996, UMEs associated with biotoxins from harmful algal blooms have become more prevalent. The majority of recent UMEs have been attributed to toxicity from domoic acid or brevetoxin.

Past and Current UMEs
The charts illustrate the data shown in the table below. Click on an image to view at a larger size in PDF format.

UMEs Per Year	UMEs Per Year by Causes

	Causes of UMEs	UMEs per Geographic Area	Species Impacted by UMEs

No.	Year	Species	Location	Cause (Category)
1	1991	Harbor seals	New York	Infectious Disease
2	1991	California sea lions	California	Infectious Disease
3	1991	Bottlenose dolphins	Florida (Sarasota)	Undetermined
4	1992	Phocids	New England	Infectious Disease
5	1992	Bottlenose dolphins	Texas	Undetermined
6	1992-1993	Pinnipeds	California	Ecological Factors
7	1993	Pinnipeds	Washington	Human Interaction
8	1994	Common dolphins	California	Undetermined
9	1994	Bottlenose dolphins	Texas	Infectious Disease
10	1996	Right whales	Florida, Georgia	Human Interaction
11	1996	Manatees	Florida (west coast)	Biotoxin
12	1996	Bottlenose dolphins	Mississippi	Undetermined
13	1997	Harbor seals	California	Infectious Disease
14	1998	California sea lions	California	Biotoxin
15	1999-2000	Bottlenose dolphins	Florida (Panhandle)	Biotoxin
16	1999-2001	Gray whales	California, Oregon, Washington	Undetermined
17	2000	California sea lions	California	Biotoxin
18	2000	Harbor seals	California	Infectious Disease
19	2001	Bottlenose dolphins	Florida (Indian River)	Undetermined
20	2001-2002	Hawaiian monk seals	Hawaii (Northwest Hawaiian Islands)	Ecological Factors
21	2002	Multispecies (common dolphins, California sea lion, sea otters)	California	Biotoxin
22	2002	Manatees	Florida (west coast)	Biotoxin
23	2003	Sea otters	California	Ecological Factors
24	2003	Large whales (primarily humpback whales)	Gulf of Maine	Undetermined
25	2003	Manatees	Florida (west coast)	Biotoxin
26	2003	Harbor seals and Minke whales	Maine	Undetermined
27	2004	Bottlenose dolphins	Florida (Panhandle)	Biotoxin
28	2004	Small cetaceans	Virginia	Undetermined
29	2004	Small cetaceans	North Carolina	Undetermined
30	2005-2006	Multi-species (manatees and bottlenose dolphins)	Florida (west coast)	Biotoxin
31	2005	Harbor porpoises	North Carolina	Undetermined
32	2005	Large whales	North Atlantic	Undetermined
33	2005-2006	Bottlenose dolphins	Florida (Panhandle)	Biotoxin
34	2006	Sea otters	Alaska	Undetermined
35	2006	Humpback whales	North Atlantic	Undetermined
36	2006	Pinnipeds	North Atlantic	Undetermined
37	2006	Harbor porpoises	Pacific Northwest	Undetermined
38	2006	Manatees	Florida (Everglades)	Biotoxin
39	2007	Bottlenose dolphins	Texas and Louisiana	Undetermined
40	2007	Cetaceans	California	Undetermined
41	2007	Manatees	Florida (SW)	Biotoxin