57. 



controlling its track. 



A comparison of the results obtained by these two 

 survey methods is possible for several areas in Oceanographer 

 Canyon where the camera-sled track coincided with the location 

 of previous ALVIN dives. A close examination of Figure 11 

 shows that in most areas there are marked differences in 

 terms of faunal composition between the results obtained by 

 these two methods. The most apparent discrepancy is that 

 the towed camera-sled does indeed underestimate the abundance 

 of corals. This difference is greatest in areas of high 

 relief when the camera-sled is towed across bathymetric 

 contours rather than along them. A closer examination of 

 the species shows that most of them are taxa that are restrict- 

 ed to hard substrates. 



On the west wall of Oceanographer Canyon the fauna 

 surveyed with ALVIN (circles with stars) consistently had 

 higher proportions of corals, than that surveyed by "Cheep 

 Tow". The corals Anthomastus agassizi-t ^ Pavamurioea grandis 

 and Aoanthogovgia armata frequently composed more than half 

 of the epifauna surveyed by ALVIN. The abundances of these 

 corals was markedly reduced in the photographs taken by "Cheep 

 Tow." The results of the survey done by camera-sled do show 

 that these corals are present in that area, but it does not 

 reflect their true abundances or relative proportion of the 

 fauna. One taxa consistently underestimated by the ALVIN 



