2010–2014 Cetacean Unusual Mortality Event in Northern Gulf of Mexico (Closed)

Overview

Under the Marine Mammal Protection Act, an Unusual Mortality Event  was declared for dolphins and whales (cetaceans) in the northern Gulf of Mexico (Texas/Louisiana border through Franklin County, FL) in early 2010.

Based on analysis of stranding data and recommendations from the UME investigative team and the Working Group on Marine Mammal Unusual Mortality Events (an advisory group of marine mammal health and biology experts), NOAA has declared the northern Gulf of Mexico cetacean UME closed. The investigation results of the cetacean UME in the northern Gulf of Mexico are available on our website. Results and publications will continue to be updated as they become available.

The temporal and spatial boundaries have been redefined to include the following:

• All cetaceans stranded in Alabama, Mississippi, and Louisiana from March of 2010–July of 2014, and
• All cetaceans other than bottlenose dolphins stranded in the Florida Panhandle (Franklin County through Escambia County) from March 2010–July of 2014. These boundaries could be adjusted in the future based upon the availability of new results or analyses.

The UME investigation and the Deepwater Horizon Natural Damage Resource Assessment have determined that the Deepwater Horizon oil spill resulted in the death of marine mammals and is the most likely explanation of the persistent, elevated stranding numbers in the northern Gulf of Mexico after the spill.

The evidence to date supports the hypothesis that exposure to Deepwater Horizon petroleum products was the most likely explanation of the adrenal and lung disease in dolphins, which has contributed to increased deaths and fetal loss among dolphins living within the oil spill footprint. While the number of dolphin mortalities in the area decreased after the peak from March 2010–July 2014, it does not indicate that the effects of the oil spill on these populations have ended.

Researchers still saw evidence of chronic lung disease and adrenal impairment even 4 years after spill (in July 2014), and saw evidence of failed pregnancies in 2015. Research into the long-term health effects of the spill on marine mammal populations is ongoing.  For more information on proposed restoration and monitoring activities please see the Final Programmatic Damage Assessment and Restoration Plan (PDARP) for the Gulf of Mexico. Additionally, more details are available on NOAA’s investigation results page.

These numbers are preliminary and may be subject to change. The UME involves 1,141 cetacean strandings in the Northern Gulf of Mexico. Five percent of the cetacean strandings were alive, while 95 percent were stranded dead.

*This number includes 13 dolphins that were killed incidental to fish related scientific data collection and one dolphin killed incidental to trawl relocation for a dredging project.

**The initial response phase ended for all four states on November 2, 2010. Response re-opened for eastern and central Louisiana on December 3, 2010 and closed again on May 25, 2011.

Brucella Infection

In addition to investigating all other potential causes, scientists investigated what role Brucella bacteria had in the UME.

Since our finding of Brucella in 5 stranded dolphins from Louisiana in 2011, scientists tested cases that showed pathological changes consistent with the fetal pneumonia or adult meningitis identified in the first five cases. A total of 68 of 210 dolphins tested positive or equivocal for Brucella. Additional information about Brucella in stranded dolphins can be found in Colegrove et al. 2016.

Learn more about Brucella infection in whales and dolphins

Data for All Stranded Cetaceans

By month/year: All stranded cetaceans (dolphins and whales) from Franklin County, FL to Louisiana and bottlenose dolphins from Louisiana to Alabama.

NOTES: Historical data are unvalidated and numbers may be subject to change as more information becomes available. Current UME data are considered preliminary and may be subject to change as more information becomes available. The data include any strandings that occurred on or before July 31, 2014 as well as 13 cases that were incidental scientific data collection takes and one take incidental to trawl relocation for a dredging project.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Average (2002-2009)	5.5	3.6	16.3	11.1	4.8	3	3.9	3.3	4.1	3.3	2.4	2
2010 Total			53	36	39	30	11	18	15	6	11	12
2011 Total	20	62	64	35	20	22	16	30	15	26	17	15
2012 Total	21	21	43	17	11	6	7	5	10	13	16	13
2013 Total	22	24	45	65	29	12	3	7	4	8	4	9
2014 Total (Jan-Jul)	14	28	30	34	24	15	8

All stranded cetaceans (dolphins and whales) from Franklin County, FL to Louisiana and bottlenose dolphins from Louisiana to Alabama, by state.

NOTES: Historical data are unvalidated and numbers may be subject to change as more information becomes available. Current UME data are considered preliminary and may be subject to change as more information becomes available. The data include any strandings that occurred on or before July 31, 2014 as well as 13 cases that were incidental scientific data collection takes and one take incidental to trawl relocation for a dredging project.

	FL Panhandle	AL	MS	LA
Average (2002-2009)	8	14	20	21
2010 (Mar-Dec)	12	21	63	135
2011 Total	8	59	111	164
2012 Total	9	30	50	94
2013 Total	7	27	51	147
2014 (Jan-Jul)	4	32	43	74

Number of strandings by month per state/region.

Number of strandings per state or region from March 2010 through July 2014.

NOTES: The red line represents the number of cetacean strandings in each region over time. The green line represents the reported number of stillborn, premature, or neonate stranded bottlenose dolphins (actual or estimated whole carcass lengths less than 115 cm) in each region over time (February of 2010 through July of 2014). The blue line represents the historical average per month calculated from 2002–2009 stranding data.

Historical data are unvalidated and numbers may be subject to change as more information becomes available. Current UME data are considered preliminary and may be subject to change as more information becomes available. The data include any strandings that occurred on or before July 31, 2014 as well as 13 cases that were incidental scientific data collection takes and one take incidental to trawl relocation for a dredging project.

Data for Stranded Bottlenose Dolphins (All Size Classes)

All stranded bottlenose dolphins from Alabama through Louisiana by month.

NOTES: Historical data are unvalidated and numbers may be subject to change as more information becomes available. Current UME data are considered preliminary and may be subject to change as more information becomes available. The data include any strandings that occurred on or before July 31, 2014 as well as 13 cases that were incidental scientific data collection takes and one take incidental to trawl relocation for a dredging project.

Data for Premature, Stillborn, or Neonatal Bottlenose Dolphins (with less than 115 cm Total Length)

Stranded bottlenose dolphins from Alabama through Louisiana with reported actual or estimated whole carcass lengths less than 115 cm (partial carcasses excluded).

NOTES: Bottlenose dolphins less than 115 cm in total length are either premature, stillborn, or neonatal.

Historical data from 2008 through present are unvalidated and numbers may be subject to change as more information becomes available. UME data are considered preliminary and may be subject to change as more information becomes available. They include any strandings that occurred on or before July 31, 2014 as well as 13 cases that were incidental scientific data collection takes and 1 take incidental to trawl relocation for a dredging project.

More Information

• Deepwater Horizon oil spill: Final Programmatic Damage Assessment and Restoration Plan and Final Programmatic Environmental Impact Statement.
• Investigation Results of the Cetacean Unusual Mortality Event in Northern Gulf of Mexico.
• Marine Mammal Health and Stranding Response Program.
• Marine Mammal Protection.
• Unusual Mortality Events.