Update on the Northern Gulf of Mexico Cetacean Unusual Mortality Event, 2010–2013: Bottlenose Dolphins (Tursiops truncatus)
IAAAM 2013
Stephanie Venn-Watson1*; Jenny Litz2; Kathleen Colegrove3; Michael Kinsel3; Lance Garrison2; Karen Terio3; Ruth Carmichael4; Erin Fougeres5; Blair Mase-Guthrie2; Ruth Ewing2; Delphine Shannon6; Steve Shippee7; Suzanne Smith8; Lydia Staggs9; Elizabeth Stratton2; Mandy Tumlin10; Teri Rowles11
1National Marine Mammal Foundation, San Diego, California 92106, USA; 2National Marine Fisheries Service, Southeast Fisheries Science Center, Miami, Florida 33149, USA; 3Zoological Pathology Program, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Maywood, IL 60153, USA; 4Dauphin Island Sea Lab and University of South Alabama, Dauphin Island, Alabama 36528, USA; 5National Marine Fisheries Service, Southeast Regional Office, St. Petersburg, Florida 33701, USA; 6Institute for Marine Mammal Studies, Gulfport, Mississippi 39502, USA; 7Emerald Coast Wildlife Refuge, Fort Walton Beach, Florida 32548, USA; 8Audubon Aquarium of the Americas, New Orleans, Louisiana 70130, USA; 9Gulf World Marine Park, Panama City Beach, Florida 32413, USA; 10Louisiana Department of Wildlife and Fisheries, Baton Rouge, Louisiana 70808, USA; 11National Marine Fisheries Service, Office of Protected Resources, Silver Spring, Maryland 20905, USA
Abstract
An unusual mortality event (UME) involving primarily bottlenose dolphins (Tursiops truncatus) in the northern Gulf of Mexico (GoM) (Alabama, Florida panhandle, Louisiana, and Mississippi) began in early 2010 and remains open. Statistical review of historically stranded dolphins in the GoM (1986–2011) was conducted. Large scale mortality years, years in which the number of stranded bottlenose dolphins by state exceeded the 90th percentile, included 2010 and 2011 for Louisiana; and 2011 for Alabama and Mississippi. Two distinct demographies within the current UME include perinates (less than 115 cm body length) in Alabama and Mississippi (early 2011) and non-perinates in Louisiana. Of 32 perinates investigated, 84% died in utero, 78% had fetal distress, and 63% had bacterial pneumonia, many of which were due to marine Brucella; preliminary data suggest a diversity of genetic sequences of marine Brucella were present in this event. Among 28 fresh dead non-perinatal UME dolphins, 39% had death-associated bacterial pneumonia from a variety of pathogens, and 56% (5/9) of dolphins more than 190 cm body length stranded near Barataria Bay, Louisiana had adrenal gland abnormalities (hypertrophy or cortical atrophy). Diagnostic tests to date do not support the UME cause to be Morbillivirus or marine biotoxins, or Brucella among non-perinates. The Deepwater Horizon oil spill has not been ruled out as a possible contributing factor to this UME, which is the longest lasting and largest dolphin mortality event in US recorded history. The undetermined etiology appears to have increased dolphins' susceptibilities to death-associated bacterial pneumonia, adrenal gland abnormalities, fetal distress, and Brucella-associated abortions.
Acknowledgements
The authors would like to thank the Southeast US Marine Mammal Stranding Network, particularly the staff of Louisiana Department of Wildlife and Fisheries, Audubon Aquarium of the Americas, Institute for Marine Mammal Studies, Dauphin Island Sea Lab, Emerald Coast Wildlife Refuge, and Gulf World Marine Park for their continued hard work during this event. We also thank the NMFS SEFSC, SERO and OPR staff, the Incident Command Post staff, those who traveled to the Gulf to assist with carcass recovery and examinations, as well as, the Working Group on Marine Mammal Unusual Mortality Events and the UME Investigative Team for their continued support.
* Presenting author