Frequent Questions: 2019 Bottlenose Dolphin Unusual Mortality Event along the Northern Gulf of Mexico
Elevated bottlenose dolphin strandings have been occurring in the Northern Gulf of Mexico including Louisiana, Mississippi, Alabama, and the panhandle of Florida (Alabama border through Franklin County) since February 1, 2019.
Why is NOAA Involved in Declaring a UME?
Conserving and restoring protected resources including marine mammals, fish, and corals is a core mission for NOAA Fisheries. NOAA Fisheries is responsible for the protection and conservation of all whales, dolphins, porpoises, seals, and sea lions under the Marine Mammal Protection Act. We depend on healthy marine species for maintaining balanced and thriving ocean ecosystems and coastal communities. NOAA Fisheries relies on the best available science to carry out the mandates of the Marine Mammal Protection Act, including reducing the negative effects of human activities on protected species and their habitats. We develop and implement plans to guide species recovery and conservation, enforce regulations against harming protected species, and conduct high-quality science focused on conservation.
What are you announcing today?
NOAA Fisheries has declared an Unusual Mortality Event (UME) for common bottlenose dolphins (Tursiops truncatus) in the Northern Gulf of Mexico including Louisiana, Mississippi, Alabama and the panhandle of Florida (Alabama border through Franklin County). The increase in strandings for this event began in February 2019 and strandings remain high.
What is an Unusual Mortality Event?
An Unusual Mortality Event 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 appointed by NOAA Fisheries in consultation with the Marine Mammal Commission and USFWS, determines that an event meets one or more of the criteria, it forwards a recommendation to NOAA’s Assistant Administrator for Fisheries to declare an UME.
What criteria have been met?
In this case, the Working Group concluded that two of the seven criteria have been met. These include the following criteria:
- A marked increase in the magnitude or a marked change in the nature of morbidity, mortality or strandings when compared with prior records.
5. Affected animals exhibit similar or unusual pathologic findings, behavior patterns, clinical signs, or general physical condition.
How widespread is this UME?
Since February, increased mortalities of common bottlenose dolphins have been observed in Louisiana, Mississippi, Alabama and the panhandle of Florida (Alabama border through Franklin County).
When did the first reports of increased strandings of bottlenose dolphins occur?
Increased strandings began in early February 2019, strandings have continued through the present and were particularly high in April and May.
How many bottlenose dolphins are involved in the event?
The event began on February 1, 2019, and there have been at least 260 confirmed stranded bottlenose dolphins documented between February 1st and May 31st. The historical average excluding previous UME years for February through May in the affected area is 57 dolphins and including previous UME years is 87 dolphins.
What are the findings in stranded animals?
Full or partial necropsy examinations have been conducted on some dolphins; however, many of the dolphins have stranded in a moderate to advanced state of decomposition, limiting the ability to collect samples to determine cause of death or descriptions of lesions. In addition, a number of dolphins have stranded in very remote locations or been reported well after the fact, limiting the ability to recover some animals for examination.
A number of the stranded dolphins have had visible skin lesions that are consistent with freshwater exposure. As determined by carcass decomposition state, samples are being collected for histopathology to describe the lesions observed in the carcasses. Additional testing of samples collected will be informed by the results of the pathology examination and will be used to detect any presence of any disease, injury, etc. as this investigation continues.
Is it common to see bottlenose dolphins with freshwater skin lesions?
During the spring season, it is not uncommon to see a reduction of salinity in bays, sounds, and estuaries and also an increase in dolphins (both live free swimming and stranded) exhibiting visible skin lesions consistent with low salinity exposure. These freshets may be a result local rainfall and/or watershed flow from upstream snow melt or flood events emptying into the bays, sounds and estuaries of the Gulf of Mexico. The Stranding Network typically may receive reports in spring-summer of some live and dead dolphins with skin lesions consistent with freshwater exposure, ranging in severity from moderate to severe.
Are the dolphins dying because of the spillway opening?
This year has been an especially wet year with high levels of rainfall in addition to the opening of the spillways due to the extreme flooding upstream. The natural event along with the flood control actions have altered the flow of freshwater into some of the bays, sounds and estuaries of the northern Gulf affecting dolphin habitat. The impacts of salinity changes on the dolphins will be investigated as a potential contributing factor to this UME. The Bonnet-Carre has been open 76 days (January-June 11, 2019) affecting areas east of the Mississippi River outflow.
What are the risks of freshwater exposure to bottlenose dolphins?
Coastal and oceanic bottlenose dolphins are typically found in high salinity from 20-35ppt; however dolphins in bays, sounds, and estuaries across the U.S. periodically experience lower salinity environments especially in the spring or early summer. In some extreme weather years, those lower salinity environments may be low and last for longer periods of time. How low the salinity goes and how long it lasts often determines along with other factors influences the severity of the impacts to dolphins. Health impacts, such as skin lesions, abnormal blood chemistry, swelling of the cornea, and eventual death, can occur in dolphins due to low salinity exposure over a period of days to weeks. These health impacts can be exacerbated in dolphins with pre-existing conditions, such as injuries, infections, poor nutrition, or immune suppression. The time from initial exposure to death is unknown and may depend on the amount of salinity change (how low), the length of exposure, whether exposure is continuous or intermittent, and the presence of any underlying health conditions or additional stressors. In addition to these potential direct impacts, alterations in prey (types, abundance and distribution) due to freshwater may have longer term secondary impacts on dolphins.
Why don't the dolphins just swim to areas of higher salinity?
Resident stocks of bottlenose dolphins in bays, sounds, and estuaries more often exhibit strong, life-long site fidelity to a small, well-defined home range and do not leave this home range despite environmental challenges that may negatively impact their health. They may redistribute within a habitat.
This area overlaps with the area affected by the Deepwater Horizon Oil Spill in 2010. Are there still health effects in the dolphins in the Northern Gulf of Mexico?
Dolphins were observed to have significant health impacts as a result of the Deepwater Horizon oil spill. These included the following health conditions: adrenal disease, lung disease, a high prevalence of blood abnormalities, and overall poor body condition. Studies indicate that not all these health conditions have fully resolved. The DWH programmatic assessment and restoration plan predicted the maximum reduction in the population due to these health conditions; for instance, in Barataria Bay, to be 51% by nine years post spill. Compromised health may make dolphins more susceptible to additional environmental stressors, such as low salinity.
Were the dolphins stranding in the 2010-2014 Northern Gulf of Mexico Cetacean UME impacted by the Deepwater Horizon Oil Spill?
The area and bottlenose dolphin stocks impacted by this UME are the same as those impacted by the northern Gulf of Mexico cetacean UME (NGUME) that occurred from March 2010 through July 2014. The NGUME involved 1,141 cetacean strandings in the Northern Gulf of Mexico, of which 85% were bottlenose dolphins.
Exposure to Deepwater Horizon petroleum products was determined to be the most likely explanation for the NGUME, which found adrenal and lung disease in dolphins, and has contributed to increased deaths and fetal loss among dolphins living within the oil spill footprint. The effects of the oil spill on these populations is ongoing. Researchers saw evidence of chronic lung disease and adrenal impairment even four years after the DWH oil 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 continuing.
Have other Marine mammals or animals been affected by this Die-off Event?
There have been reports of increased strandings of sea turtles in LA and MS and investigations into the causes of those mortalities are underway. Strandings are above the running five and ten year averages, but are lower than documented in some previous years. We DO NOT suspect that the current sea turtle strandings are related to freshwater exposure - we do, however, have concerns that decreased salinity will have longer term effects on sea turtle prey and habitat.
What is the current dolphin population along the Northern Gulf of Mexico?
Seventeen stocks of bottlenose dolphins co-occur in the UME area along the Northern Gulf of Mexico. These include two coastal stocks (western coastal and northern coastal) and fifteen bay, sound, and estuary stocks (listed below):
1. Sabine Lake
2. Calcasieu Lake
3. Vermilion Bay/West Cote Blanche Bay/Atchafalaya Bay
4. Terrebonne Bay/Timbalier Bay
5. Barataria Bay
6. Mississippi River Delta
7. Mississippi Sound/Lake Borgne/Bay Boudreau
8. Mobile Bay/Bonsecour Bay
9. Perdido Bay
10. Pensacola Bay/East Bay
11. Choctawhatchee Bay
12. St. Andrew Bay
13. St. Joseph Bay
14. St. Vincent Sound/Apalachicola Bay/St. George Bay
15. Apalachee Bay (the very western edge of this stock borders a very small part of the eastern edge of Franklin County, FL)
How Many other Bottlenose Dolphin UMEs have previously occurred in the GOM?
Twelve UMEs involving bottlenose dolphins have occurred in the U.S. EEZ of the Gulf of Mexico from 1991 to the present. Five of these events were attributed to red tide toxins (brevetoxin), at least one to morbillivirus infection, and one to the Deepwater Horizon oil spill, the causes of the other five events were undetermined. Five UMEs occurred in Texas, five UMEs occurred in Florida, one occurred in Mississippi, and one occurred across the Northern Gulf of Mexico.
What are the next steps in the investigation now that an UME has been declared?
As part of the UME investigation process, a team of scientists (investigative team) is assembled to coordinate with the working group to review the data collected and determine potential next steps. The investigative team will develop an investigative plan and coordinate with other ongoing UME investigations. The investigation may require weeks, months, or even years of response, data collection, analysis, and interpretation.
What additional resources are now available to pursue the investigation, since an UME has been declared?
An UME declaration provides additional expertise from the working group (an international and multidisciplinary team of scientists) and additional stranding response partners, as well as access to some additional funding through the National UME Contingency Fund. In addition, a detailed investigative plan will be developed that may include more targeted necropsies, additional targeted analyses of samples and diagnostic pathology services. Finally, through the UME process all findings and interpretations may undergo national and international scientific review.
Are additional resources from the DWH funds available for response and investigations?
The stranding networks in three (FL, AL, MS) of the four affected states receive support from the Gulf Environmental Benefit Fund (GEBF) from the National Fish and Wildlife Foundation. These funds provide support for personnel, some analyses, and response activities including necropsies. Louisiana is the only state in the UME in which the stranding network does not receive GEBF funding for stranding response activities. Support for marine mammal stranding networks has not yet been analyzed for specific funding under the DWH NRDA, therefore no funds are currently available from the NRDA restoration program.
Will you be collecting additional biological and environmental information?
Stranding network partners will continue to collect and analyze samples as needed to evaluate the situation. The Investigative team will determine what additional information is needed and will review results as they come in to inform additional data collection and sampling.
When will you have some results to share?
The Investigative Team are beginning to develop an investigative plan. UME investigations typically take many months or longer to complete. Investigative results will be shared with the UME Working Group for evaluation and final cause, if determinable. In the meantime, we will continue to update our website with current dolphin stranding numbers during this event. We will share a final determination of whether or not a cause was determined and what that cause or contributing factors as soon as possible.
What is the risk to humans?
It is best not to touch or handle live or dead stranded marine mammals and to report them to NOAA’s Southeast marine mammal stranding network as soon as possible. Bottlenose dolphins are wild animals and may injure people if approached closely, additionally, marine mammals can transmit diseases to humans.
Are there any risks to pets?
Pets should always be kept away from marine mammals, particularly diseased or dead marine mammals.
Are the Northern Gulf of Mexico Unusual Mortality Event and the Southwest Florida Dolphin Unusual Mortality Event connected or related at all?
No, currently we do not believe the causes of the two UMEs are connected. The Southwest Florida UME is attributed to a red tide bloom in the eastern Gulf of Mexico, which caused illness and death in several species of marine wildlife (dolphins, manatees, fish, and birds).
The cause of the Northern Gulf of Mexico UME has not yet been determined but it is not currently believed to be caused by a red tide bloom.
Where can I find additional information on bottlenose dolphins and other Unusual Mortality Events?
What should people do if they encounter a dead dolphin floating or stranded on the beach?
Please immediately contact your local stranding network or local authorities to report a live or dead stranded dolphin:
- For the Southeast Region, call 877-WHALE HELP (877-942-5343).
- Do not touch the dolphin.
- Don’t allow pets to approach the dolphin.
- Observe the animal from a safe distance of 100 yards (safe for you and the animal).
What can I do to help the investigation?
The most important step members of the public can take to assist investigators is to immediately report any sightings of live dolphins in distress or stranded or dead dolphins. Call the Southeast Marine Mammal Stranding Hotline at 877-WHALE HELP (877-942-5343), or mariners should contact the U.S. Coast Guard on VHF Channel 16 if they do not have cell service. Do not approach or touch the dolphin.
Additionally, the public may use Pay.gov to donate to the UME Contingency Fund for this or other UMEs as this helps cover costs incurred by the Marine Mammal Stranding Network and the investigation. The public can also provide assistance through contact with their local network.
What should people do if they witness harassment or any marine mammal violation in the water or on the beach?
To report violations please contact NOAA’s Office of Law Enforcement at (800)853-1964.
What is the UME Contingency Fund?
MMPA section 405 (16 USC-1421d) establishes the Marine Mammal Unusual Mortality Event Fund describing its purposes and how the public can donate to the fund. According to the MMPA, the fund: “shall be available only for use by the Secretary of Commerce, in consultation with the Secretary of the Interior:
- To compensate persons for special costs incurred in acting in accordance with the contingency plan issued under section 1421c(b) of this title or under the direction of an Onsite Coordinator for an unusual mortality event.
- For reimbursing any stranding network participant for costs incurred in preparing and transporting tissues collected with respect to an unusual mortality event for the Tissue Bank.
- For care and maintenance of marine mammal seized under section 1374(c)(2)(D) of this title.”
The National Contingency Plan for Response to Unusual Marine Mammal Mortality Events outlines the types of expenses that are reimbursable under the fund and the process for requesting reimbursement.
Learn more about the UME Contingency Fund.