presence of a "red tide" bloom in North Carolina between late 

 October 1987 and early March 1988 raised concern about the 

 possible involvement of brevetoxin, a fat-soluble biotoxin 

 produced by the dinof lagellate, Ptychodiscus brevis, in the 

 die-off. To determine whether red tide biotoxins may have 

 caused or contributed to the unusual bottlenose dolphin 

 mortality, the Commission provided funds to an investigator 

 at the University of Miami to analyze samples collected from 

 three species of fish commonly preyed on by bottlenose dolphins. 

 The contract report, which was received in June 1988, indicated 

 that, of the species tested (Spanish mackerel, silver trout, and 

 menhaden) , biotoxins were found in menhaden and only in the 

 viscera of the animals. These results indicated little 

 potential for intoxication in humans, and only those animals that 

 consume menhaden whole are at potential risk. 



As noted in the Commission's previous Annual Report, a 

 wide variety of pathogenic bacteria were isolated from animals 

 that stranded. Also evidence of papova viruses and herpes- 

 like particles were found in tissue samples from several of 

 the stranded dolphins and, in samples from some animals, high 

 levels of organochlorides were detected. None of the isolated 

 bacteria, viruses, or environmental contaminants have been 

 found consistently in animals that died, suggesting that while 

 they may have contributed to or caused the deaths of some 

 animals, they were not the primary cause of the die-off. 



At the end of the year, toxicological and other analyses 

 undertaken to determine the cause of the die-off were being 

 concluded. A final report on this aspect of the investigation 

 is expected to be completed and submitted to the Marine Mammal 

 Commission and the National Marine Fisheries Service at the 

 end of January 1989. 



Population Status 



Data from population studies done in the late 1970s and 

 early 1980s suggested that there could be two more or less 

 discrete stocks of bottlenose dolphins along the U.S. east 

 coast — a nearshore stock that moves north to the New 

 Jersey/New York Bight area in the spring and south to the 

 Georgia/Florida area in the fall, and an offshore stock that 

 occurs primarily along the 100-fathom depth contour between 

 Georges Bank in the north and Cape Hatteras in the south. 

 Data from the die-off investigation were insufficient to judge 

 when, where, and how many animals might have been affected. 

 Therefore, as noted above, the National Marine Fisheries Service 

 began a series of coastal and offshore aerial surveys in the 

 fall of 1987 to better determine the distribution, number, 

 sizes, composition, and movements of dolphin pods along the 

 mid-Atlantic coast and to determine and monitor the number of 



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