SECTION V 



ENVIRONMENTAL FACTORS 



Robert A, Blaylock 



Southeast Fisheries Science Center 



Miami Laboratory 



75 Virginia Beach Drive 



Miami, FL 33149 



Background 



The National Marine Fisheries Service monitors marine mammal mortalities in the 

 Gulf of Mexico with the cooperation of the Southeast Marine Mammal Stranding Network 

 (SEUS). This is a mainly volunteer network of federal, state, and imiversity researchers 

 having varying levels of expertise and resources. In January-March 1990, bottlenose dolphin, 

 Tursiops truncatus, stranding in the northern Gulf of Mexico received an unusually high 

 degree of pubhc attention. The highest incidence of bottlenose dolphin stranding was 

 reported in Texas. This may reflect a higher level of detection and reporting effort in Texas 

 rather than a higher mortality rate; however, the relatively large Texas data base allowed 

 analysis of bottlenose dolphin stranding in relation to the physical environment. This study 

 examined environmental variables and the Texas bottlenose dolphin stranding record for 

 relationships which might account for the 

 high stranding incidence reported in early 

 1990. 



Methods 



Environmental factors 



The Texas Gulf of Mexico coast was 

 stratified for analysis into five statistical 

 zones of equal lengths of shoreline totahng 

 approximately 556 km (300 nm) and 

 extending from north of Galveston to the 

 U.S.-Mexico border (Areas I-V, Figure 1). 

 Bottlenose dolphin stranding records listing 

 the species stranded, date of discovery, and 

 location of the stranding and other 

 pertinent information were obtained firom 

 SEUS and the Smithsonian Institution 



TEXAS 



GULF 

 OF 



MEXICO 



Fignre 1. Locations of environmental dau stations along Texas coaxt. 

 Filled circles show Elunan transport stations and unOlled circles show 

 temperature data station locaiioiis. 



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