FISHERY BULLETIN: VOL. 84, NO. 2 



with high metabolic rates and accordingly high feed- 

 ing rates. They are estimated to consume prey equi- 

 valent to 1.5-4% of their body weight daily (Sergeant 

 1969; Lockyer 1981), with some estimates for 

 smaller species as much as 10% of body weight per 

 day (eg. Smith and Gaskin 1974). The CETAP study 

 concluded that cetaceans "would be expected to feed 

 virtually every day while in the study area" and that 

 "each species of cetacean was likely feeding, either 

 at the surface or below, in any area in which it was 

 seen regularly" (CETAP 1982, p. 417). For the pur- 

 poses of the current study, we have also followed this 

 reasoning and assumed that a habitat which is be- 

 ing occupied by one or more cetacean species is 

 therefore being utilized by those species as a feed- 

 ing area. 



METHODS 



The CETAP study area was defined as the waters 

 of the U.S. continental shelf north of Cape Hatteras, 

 from the shoreline to 5 nmi (9.3 km) seaward of the 

 1,000 fathom (1,829 m) isobath. Surveys were con- 

 ducted from October 1978 through January 1982. 

 Data collected from two types of surveys have been 

 used in this analysis: 



1) Dedicated aerial surveys: Random transect 

 aerial surveys were conducted in defined blocks 

 within the study area, including both regular surveys 

 throughout the year and special surveys targeted at 

 endangered species, particularly right whales. The 

 primary objective of these surveys was to estimate 

 the absolute abundance, e.g., the total number of in- 

 dividuals in the population, of each species in the 

 study area, using line transect census methods 

 (Burnham et al. 1980; Scott and Gilbert 1982). This 

 methodology requires consistent use of rigorously 

 standardized sampling, e.g., use of the same plat- 

 form, even allocation of sampling across the different 

 blocks, and random selection of transects within a 

 block. 



The two aircraft used for these surveys were a 

 Beechcraft 3 AT-11 and a Cessna 337-G Skymaster, 

 both twin-engine planes. The ATI 1 crew consisted 

 of a pilot, a navigator, and four observers; two 

 observers at a time were stationed in a clear acrylic 

 observation bubble in the nose of the plane The Sky- 

 master carried a pilot, a navigator, and two observ- 

 ers, who sat in the rear seats and watched out the 

 side windows. All surveys were conducted at an 



'Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



altitude of 750 ft (229 m) and a groundspeed of 120 

 kn (222 km/h). 



For any particular survey, a series of parallel track 

 lines was flown. For the regular surveys, the lines 

 sampled were randomly chosen from a pool of lines 

 running northwest-southeast (roughly perpendicular 

 to the bathymetry) and spaced at 2 nmi intervals 

 throughout the block to be sampled. For the en- 

 dangered species surveys, the lines were systema- 

 tically spaced at a predetermined interval, with the 

 first line placed at a randomly determined distance 

 from the edge of the block. 



2) Platforms of opportunity (POP) surveys: Trained 

 observers were placed aboard various ships and air- 

 craft operating within the study area in order to col- 

 lect distributional data to supplement the dedicated 

 surveys. The platforms most often used included 

 Coast Guard cutters, U.S. and foreign oceanographic 

 and fisheries research vessels, and Coast Guard fish- 

 eries patrol and thermography aircraft. The track 

 of the ship or aircraft was wholly determined by its 

 primary mission. These data could not be used in 

 abundance estimation because effort was not al- 

 located randomly or evenly, and the platforms used 

 were not exactly comparable 



Observers on both types of surveys recorded a 

 variety of information. The data collected included 

 date, time, latitude and longitude, platform heading, 

 beginning and end of periods when the observer(s) 

 were actively on watch, and environmental informa- 

 tion (air temperature, water temperature, depth, 

 weather, visibility, sea state, wind direction, and 

 cloud cover). The data were recorded at each sight- 

 ing, as well as at periodic intervals (typically 5 min 

 for aerial and 30 min for shipboard surveys) during 

 all on-watch periods. This allowed for subsequent 

 reconstruction of flight-cruise tracks. Additional 

 data recorded at sightings included species, reliabil- 

 ity of identification, number of animals, distance 

 from the platform, animal heading, and behaviors. 



The data were transcribed from the field forms 

 to coding forms, keypunched, and input to a com- 

 puter data base A number of quality control steps 

 were included in the process, and all discovered er- 

 rors were corrected. In addition to the two types of 

 survey data described above, historical sighting data 

 collected prior to CETAP and opportunistic sight- 

 ing data provided by fisherman, mariners, whale- 

 watchers, fish-spotters, pilots, etc are included in the 

 CETAP data. None of these data have associated 

 track-line information, and are therefore not in- 

 cluded in this paper. After completion of the CETAP 



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