Matagorda Bay during January, 1990. The delay in stranding recovery reporting (required 

 within 30 days after recovery) resulted in a lag in recognizing the event. Although contacts 

 with the SEUS network coordinator were in place before the event, SEFC contacts with the 

 network were limited, and most were established during the mortality event. The lack of 

 contacts had a impact on recognizing the event, and thus determining the scope of the event. 



The pre-existing database had a direct impact on the type and extent of analyses that 

 could be done with the 1990 database. For example, the lack and/or inconsistency of life 

 history tissue collection (teeth, reproductive tracts) limited the breadth of the age structure 

 analysis and eliminated any examination of reproductive history. The inconsistency in 

 stranding recovery efforts, and/or the lack of a measure of stranding reporting and recovery 

 efforts, reduced the statistical strength of inter-aimual and other comparisons of stranding 

 rates. Obviously, the lack of information on the effects and levels of contaminants and 

 biotoxins in healthy bottlenose dolphins, and the lack of information on levels in the pre- 

 1990 sample constrained the extent of the analyses on contaminants and biotoxins. 



The SEFC implemented a bottlenose dolphin monitoring program in 1987 (Scott and 

 Hansen 1989). This program is designed to detect a halving or doubling in abundance. The 

 monitoring program did not detect such a decline in abimdance after the mortality event. 

 However, smaller scale variations in abundance are much more difficult to detect. In 

 addition, the scope of the aerial surveys conducted during 1990 was limited, and thus 

 weakened any conclusions relative to 1990 and prior abundance levels. But it is not clear 

 that "unlimited" surveys would have strengthened any conclusions. 



Although the investigation was not successful in conclusively identifying a single factor 

 (or multiple factors) as a cause of the anomalous stranding event, several suspicious factors 

 were identified. In addition, the investigation identified weaknesses, explored new methods 

 and resulted in the implementation of several efforts which will improve future 

 investigations. These include: a more thorough statistical treatment of stranding fi-equencies, 

 correlations with envirormiental variables, and comparisons of two methods of assessing 

 stranding frequency. Stranding protocols have been refined and further standardized, and 

 the stranding networks have been augmented. The baseline data collected during this 

 investigation will be invaluable in the evaluation of future episodes of mortality among 

 bottlenose dolphins. The process of this investigation identified critical areas where the 

 required information to understand patterns of bottlenose dolphin was lacking, and has 

 resulted in the development of a plan of action which is described below. 



Recommendations and SEFC Program 



The 1990 bottlenose dolphin anomalous mortality event in the Gulf of Mexico 

 illustrated that the SEUS network was not well prepared to mount an adequate response 

 to increased strandings. Furthermore, gross inconsistencies in regular data collection and 

 reporting among Network participants have resulted in a lack of consistent baseline 

 information and the inability to monitor the stranding rate in a timely fashion. These 



91 



