Felley and Vecchione: Nekton habitat on the continental slope of North Carolina 



263 



used in the analyses (not the launch and recovery 

 times of the dives). The videotapes were recorded as 

 the submersible cruised along the bottom, generally 

 at a speed of 0.5-1 knot (ca. 25-50 cm/sec). The cam- 

 era faced forward and down and was not panned or 

 moved during the recording of videotape sections 

 used for analysis. At times the submersible stopped 

 to deploy experiments or pick up samples and at other 

 times moved away from the bottom. We recorded data 

 from video images only during periods when the sub- 

 mersible was moving and the bottom was clearly vis- 

 ible. During these periods, we quantified environ- 

 mental variables and counted individuals of nekton 

 species during 1-minute intervals. If the submers- 

 ible stopped or moved away from the bottom during 

 an interval, that interval was discarded. We did not 

 start measuring again until the submersible began 

 moving steadily and the bottom was clearly visible. The 

 bottom topography at the Cape Hatteras site was ex- 

 tremely complex, with gullies, walls, and flat expanses. 

 Only videotapes of flat areas were used for the analy- 

 sis. The videotapes of Cape Lookout dives included only 

 broad expanses of flat slope. 



Environmental variables recorded are listed in 

 Table 2 and included holes, mounds, and tubes. Holes 

 and mounds are indicators of infaunal activity. Holes 

 were generally 1-3 cm in diameter and mounds gen- 

 erally >10 cm in diameter. Tubes were 5-10 cm in 

 length and most often curved, sometimes with both 

 ends touching the substrate. Objects classified as 

 tubes were identified (Schaff 1 ) as those of polycha- 



etes and foraminifera (Bathysiphon spp.). Further 

 characterization of sediment samples from these 

 dives can be found in Levin ( 1991) and Gooday et al. 

 (1992). Holes, mounds, and tubes were coded as fol- 

 lows: = none visible during the whole interval; 1 = 

 no more than a total of 1 or 2 visible during the whole 

 interval; 2 = 1 or 2 visible at all times during the 

 interval; 3 = several always visible at any time in 

 the interval, but countable; 4 = too many to count in 

 the interval. Category 4 coded those situations where 

 the environmental feature was so densely distributed 

 that individual features were obscured by others 

 nearer the camera. Other coded variables were gas- 

 tropod/echinoderm tracks ( grooves in the substrate), 

 sea grass detritus/Z/ya/moecia tubes, and sargassum 

 detritus. These were coded 1 or for presence or ab- 

 sence in the interval; e.g. a value of 1 was assigned 

 to the interval whenever one or more tracks were 

 observed. Long thin dark objects that appeared to be 

 bits of sea grass detritus might also include tubes of 

 the polychaete Hyalinoecia (Schaff 2 ). Such objects are 

 referred to as "grass detritus" in this study. Finally, 

 we counted raw numbers of small anemones, large 

 anemones, gastropods, and crinoids. Small anemo- 

 nes probably represented Actinauge verrilli and large 

 anemones may be Bolocera sp. (Levin 3 ). Gage and 

 Tyler (1991) give excellent descriptions of epifaunal 

 and infaunal organisms and benthic features simi- 

 lar to those listed above. 



1 Schaff. T. Natl. Mar. Fish. Serv., Silver Spring, MD. Personal 

 commun., 1992. 



2 Schaff, T. Natl. Mar. Fish. Serv., Silver Spring, MD. Personal 

 commun., 1993. 



3 Levin, L. Scripps Institution of Oceanography, La Jolla, CA. 

 Personal commun., 1992. 



