METHODS 



The methods utilized can be viewed in relation to the first three objectives of the 

 Pilot Study. Objective one requires survey procedures generally applicable to the study 

 of marine mammals, birds, and turtles. Objective two involves data management and 

 analysis, and objective three requires methodological details specific to the preliminary 

 surveys. 



OBJECTIVE ONE: GENERAL SURVEY PROCEDURES 

 Survey Design 



The survey design was based on a replicate model allowing the collection of a 

 hierarchical data set which could be analyzed in a variety of ways. It was developed for 

 the Pilot Study in consultation with Mr. Stephen Leatherwood of Hubbs-Sea World 

 Research Institute. The design reduces sampling bias and "dead time" (travel to and from 

 sampling units) between transects while enhancing statistical reliability and 

 identification of environmental correlates. It is also suited to a large and complex study 

 area such as the OCS areas of the southern United States. 



Individual subunits with borders of approximately 111 km (60 nmi) on the shoreline 

 and extending 222 km (120 nmi) perpendicular to the shoreline were sampled using 

 transect legs 111 and 222 km long. Six legs were flown per day at intervals of 18 km (10 

 nmi) and parallel to the long axis of the subunit. Replicates were flown on two 

 successive days resulting in a total of 18 transects (total survey length 2,664 km per 

 subunit). Transects were randomized with regard to (1) sampling order, (2) subunit 

 section (north or south boundary), (3) exact starting position, (4) flight altitude (91 and 

 228 m), and (5) observer position within the aircraft. Transect lengths of 111 and 222 km 

 were used in a 2:1 ratio, but aircraft altitudes of 91 and 228 m were flown with equal 

 frequency. A hypothetical subunit depicting the flight path for one day is shown in 

 Figure 2. Aircraft ground speed was constant at 222 km per hour (120 kn). Flights began 

 at approximately 0800 hrs. and were terminated if the sea state conditions reached a 

 Beaufort 4 or higher. A minimum of 6 hours per day was required to complete six 

 transects. 



Weather conditions posed a particularly difficult problem in marine censusing, and 

 not all surveys could be conducted under optimum conditions. Solar glare and rough seas 

 were two problems for which no suitable solutions have been advanced. At Beaufort 4 

 large waves and numerous whitecaps impaired visibility by creating a visual distraction. 



