Marine Mammal Unusual Mortality Events

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	Bottlenose Dolphins (Tursiops truncatus) Photo: NMFS Southwest Fisheries Science Center California Sea Lion (Zalophus californianus) Photo: NMFS National Marine Mammal Laboratory

Overview
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 45 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.

The states with the most declared UMEs are:

1. California
2. Florida

The most common species involved in UMEs are:

1. Bottlenose dolphins
2. California sea lions
3. manatees

Causes have been determined for 24 of the 45 UMEs documented since 1991. Causes of UMEs include:

• 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 [pdf] or brevetoxin [pdf].

Past and Current UMEs
The charts illustrate the data shown in the table below. Click on an image to view a larger size in PDF format. A text version of the charts [pdf] is also available.

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)
46	2008	Bottlenose dolphins	Florida (Indian River)	Undetermined
45	2008	Common dolphins, Atlantic while-sided dolphins	North Carolina- New Jersey	Undetermined
44	2008	Bottlenose dolphins	Texas	Undetermined
43	2007	Guadaloupe fur seals	Nothwest	Undetermined
42	2007	Large whales	California	Human Interaction
41	2007	Manatees	Florida (SW)	Biotoxin
40	2007	Cetaceans	California	Undetermined
39	2007	Bottlenose dolphins	Texas and Louisiana	Undetermined
38	2006	Manatees	Florida (Everglades)	Biotoxin
37	2006	Harbor porpoises	Pacific Northwest	Undetermined
36	2006	Pinnipeds	North Atlantic	Undetermined
35	2006	Humpback whales	North Atlantic	Undetermined
34	2006	Sea otters	Alaska	Undetermined
33	2005-2006	Bottlenose dolphins	Florida (Panhandle)	Biotoxin
32	2005	Large whales	North Atlantic	Undetermined
31	2005	Harbor porpoises	North Carolina	Undetermined
30	2005-2006	Multi-species (manatees and bottlenose dolphins)	Florida (west coast)	Biotoxin
29	2004	Small cetaceans	North Carolina	Undetermined
28	2004	Small cetaceans	Virginia	Undetermined
27	2004	Bottlenose dolphins	Florida (Panhandle)	Biotoxin
26	2003	Harbor seals and Minke whales	Maine	Undetermined
25	2003	Manatees	Florida (west coast)	Biotoxin
24	2003	Large whales (primarily humpback whales)	Gulf of Maine	Undetermined
23	2003	Sea otters	California	Ecological Factors
22	2002	Manatees	Florida (west coast)	Biotoxin
21	2002	Multispecies (common dolphins, California sea lion, sea otters)	California	Biotoxin
20	2001-2002	Hawaiian monk seals	Hawaii (Northwest Hawaiian Islands)	Ecological Factors
19	2001	Bottlenose dolphins	Florida (Indian River)	Undetermined
18	2000	Harbor seals	California	Infectious Disease
17	2000	California sea lions	California	Biotoxin
16	1999-2001	Gray whales	California, Oregon, Washington	Undetermined
15	1999-2000	Bottlenose dolphins	Florida (Panhandle)	Biotoxin
14	1998	California sea lions	California	Biotoxin
13	1997	Harbor seals	California	Infectious Disease
12	1996	Bottlenose dolphins	Mississippi	Undetermined
11	1996	Manatees	Florida (west coast)	Biotoxin
10	1996	Right whales	Florida, Georgia	Human Interaction
9	1994	Bottlenose dolphins	Texas	Infectious Disease
8	1994	Common dolphins	California	Undetermined
7	1993	Pinnipeds	Washington	Human Interaction
6	1992-1993	Pinnipeds	California	Ecological Factors
5	1992	Bottlenose dolphins	Texas	Undetermined
4	1992	Phocids	New England	Infectious Disease
3	1991	Bottlenose dolphins	Florida (Sarasota)	Undetermined
2	1991	California sea lions	California	Infectious Disease
1	1991	Harbor seals	New York	Infectious Disease