CHAPTER IV 



DIE-OFF OF BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS ) 



The bottlenose dolphin is the most common cetacean species 

 in coastal waters off the mid and south Atlantic coastal states. 

 Prior to 1987, an average of about 12 dead bottlenose dolphins 

 a year washed up on beaches from New Jersey to Cape Hatteras. 

 In June 1987, large numbers of animals began to die and wash 

 up on New Jersey beaches. This unprecedented mortality con- 

 tinued throughout 1987 and into 1988, and moved southward 

 with the seasonal migration of the species. 



During an eleven-month period beginning in June 1987, more 

 than 740 bottlenose dolphins washed up on beaches along the 

 Atlantic coast from New Jersey to Florida. In early February 

 1988, an aerial sighting of nine dolphin carcasses on Horn 

 and Petit Bois Islands in the Mississippi Sound raised fear 

 that whatever was causing the mortality might have spread 

 into the Gulf of Mexico. However, there have been no subsequent 

 reports of possible unusual mortality of bottlenose dolphins 

 in the Gulf of Mexico, suggesting that the problem has not 

 spread to that region. Information concerning the die-off 

 and activities undertaken by the Marine Mammal Commission and 

 other agencies in response to the event are described below. 



Background 



As noted in its previous Annual Report, the Marine Mammal 

 Commission learned of the die-off in July 1987 when unusually 

 high numbers of bottlenose dolphins began washing up on beaches 

 in Virginia. The Commission immediately consulted the National 

 Marine Fisheries Service and a number of persons expert in 

 bottlenose dolphin biology and disease. The Commission asked 

 Joseph R. Geraci, V.M.D., Ph.D., at that time a member of its 

 Committee of Scientific Advisors on Marine Mammals and an 

 expert in marine mammal husbandry and disease, to organize 

 and lead an investigation to try to determine the cause or 

 causes of the die-off. 



The Commission also made arrangements with other Federal 

 agencies to help in the investigation. The Department of 

 Agriculture's Animal and Plant Health Inspection Service was 

 asked and agreed to conduct bacterial and viral isolation 

 studies and other analyses to determine whether pathogenic 

 organisms, environmental contaminants, or biological toxins 

 were causing or possibly contributing to the die-off. The 

 Smithsonian Institution agreed to continue collecting basic 

 morphological data from the stranded animals, and the U.S. 



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