Section 4 



COLLECTION OF RELEVANT BASELINE DATA FOR COMPARISION 

 WITH RESULTS OF INTERVIEW PROGRAM 



In order to determine whether or not offshore oil activities are affecting the 

 distribution of marine mammals, it is necessary to know what density of marine 

 mammals would be expected in the area if no oil activities were present. 



A literature search rapidly determined that by far the most complete and 

 quantitative data available on marine mammals in the Southern California Bight 

 are from the Bureau of Land Management's (BLM's) 3-year marine mammal program. 

 These data have not yet been published, but BLM will allow the report to be 

 examined in their offices, and they will permit the relevant portions to be 

 photocopied. 



The BLM report gives seasonal sightings for each species of marine mammal on a 

 grid pattern of the Southern California Bight. From these sighting data, the 

 BLM investigators has regressions of densities of each species versus various 

 environmental parameters. From those regressions which were statistically 

 significant an overall density pattern, which correlated a species' abundance 

 to the distribution of the significant environmental parameters, was projected 

 for each marine mammal species in the Bight. Densities of each species of 

 marine mammal around the oil platforms as estimated by the sighting cards can 

 then be compared to the density of the marine mammal species in the appropriate 

 quadrat as estimated by BLM. The sighting card program determines whether the 

 density calculated by the sighting cards is within the range of density estim- 

 ates calculated by BLM for that quadrat during the same season. 



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