INTRODUCTION 



The Southeast U.S. Marine Mammal Stranding Network (SEUS) was organized in 

 1977 to document and salvage marine mammal strandings along the U.S. coast from Texas 

 to Virginia (for a review of the network, see Odell, 1991). Most of the Network participants 

 are volunteers, and stranding reporting and salvage efforts vary considerably. For example, 

 salvage efforts range from nearly none along Louisiana to nearly 100% along Texas. 

 Although the salvage efforts are not consistent, stranding records may provide an index of 

 mortality rates and have been used to estimate the potential effects of anomalous mortality 

 events (Scott et al., 1988). Nearly all of the stranding reports and specimens used in the 

 investigation of 1990 strandings were provided by the participants of the SEUS. A list of 

 specimens collected during the mortality event imder investigation is provided in Appendix 

 I. The specimens are listed by stranding date, and information is provided on location, sex, 

 length, tissues collected, and analyses conducted. 



The investigation was initiated due to reports that higher than normal numbers of 

 bottlenose dolphins were stranding along the U.S. Gulf coast. Begiiming in early 1990, a 

 number of stranding and mortality observations of bottlenose dolphins were made. There 

 was a mass dieoff of 23 dolphins in January in Matagorda Bay, Texas, that may have been 

 caused by unusually cold weather (Miller, 1991). A higher level of strandings than the prior 

 4-year average was observed in the Gulf along the coasts of Rorida, Alabama, Mississippi, 

 and Texas beginning in January. Floating dolphin carcasses were consistently observed during 

 January and February while NMFS observers were on transit to deep water aerial survey 

 study areas in the central northern Gulf of Mexico. As a result of all of these observations, 

 the SEFC notified the NMFS Office of Protected Resources and the MMC of the 

 observations and began intensified monitoring of the strandings and initiated an investigation 

 of the cause and extent of the strandings. 



Higher munbers of dolphins than the prior 4-year average continued to strand from 

 the Florida panhandle to Texas during February and March, 1990. Strandings decreased to 

 average or below 



average along the 

 Texas coast after 

 March, 1990, but 

 continued to occur 

 sporadically at 

 higher than 

 average levels 

 along the 

 Mississippi, 

 Alabama, and 

 Florida coasts 

 from February 

 through May, 



TaMc L Northern Gulf of Mexico 1990 bottlenose dolphin strandings by slate and month. 



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