Aerial Surveys 



Keith D. Mullin 



Southeast Fisheries Science Center 



Mississippi Laboratory 



Pascagoula Facility 



3209 Frederic Street 



Pascagoula, MS 39567 



Methods 



Survey Blocks 



Aerial surveys were conducted in response to two events: the 1990 bottlenose dolphin 

 mortality event and the oil spill from the oil tanker MEGABORG. The surveys completed 

 in response to the mortality event were conducted in block 154 during March, 1990. The 

 surveys associated with the oil spill were conducted during Jime, 1990 in the vicinity of the 

 MEGABORG and with one exception (block "B") duplicated survey blocks studied by Scott 

 et al. (1989) (Figure 1): 152 - 1,296 km^, 153 - 1,588 km^, 053 - 16,292 km^ and 154 - 11,040 

 km^. Block "B", a 5,850 km^ area in the immediate vicinity of the MEGABORG was also 

 surveyed (see Section II, Figure 1). Sampling methods for all surveys were similar. 



Sampling 



Aerial surveys using line transect methods (Bumham et al. 1980) were used to sample 

 the survey blocks. The sampling strategy was similar to that presented by Scott et al. (1989). 

 Transects were selected randomly and were placed perpendicular to water depth isobaths. 

 Samples were designed to sample 7.5% of the surface area of blocks 152, 153, and 154, and 

 5% of 053. 



Survey flights were conducted during daylight hours from 22-24 March 1990 and 14-18 

 June 1990 when the weather was clear to partly cloudy and the Beaufort Sea State was 3 or 

 less. The survey platform was a DeHavilland (DHC-6) Twin-Otter aircraft maintained and 

 operated by NOAA's Aircraft Operations Center. The aircraft had a large plexiglas bubble 

 window on each side which allowed for an unobstructed view of the transect line. 



Transects were surveyed from an altitude of 230 m (750 feet) at an airspeed of 204 

 km/hour (110 knots). The flight crew consisted of a NOAA pilot and copilot, and 3 

 experienced NMFS observers. While surveying transects, one observer was stationed at each 

 bubble-window. The third observer entered data on a laptop computer. The computer was 



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