A-7 



Qualitative information concerning the occurrence of 

 selected taxa was obtained from NMFS (Woods Hole) . 



Unfortunately there are large data gaps in the submer- 

 sible coverage. Most of the usable photographic transects 

 were restricted to the submarine canyons. This allows 

 little opportunity for strict comparison between canyon and 

 slope fauna at equivalent depths. Another problem is that 

 the footage from many of the earlier ALVIN dives is lost or 

 footage was not even taken. Additionally, there is vir- 

 tually no available photographic record between the depths 

 of 400 to 800 meters and coverage at depths greater than 

 2000 meters is very sparse. 



The photographic method for estimating abundance and 

 distribution of epibenthos has various advantages over 

 trawling or motion pictures. Both of these other methods 

 tend to underestimate epifaunal density, whiles direct visual 

 observation tends to overestimate it (Grassle et al., 1975). 

 Barham, Ayer and Boyce (1967) compared measures of epifaunal 

 density obtained by still photographs and 16 mm cinemapho- 

 tography along a transect in the San Diego Trough. The 

 densities obtained from examination of the still photographs 

 were nearly twice as high as those obtained from a study of 

 the motion pictures. The investigators attributed this 

 difference to the more critical examination possible with 

 camera stills. A comparison of densities estimated from 

 trawls versus still photographs shows that photographs 



