2. 



(1969) and Rowe (19 71) using combined camera lowerings and 

 trawls resulted in the finding that the dominant species of 

 continental slope assemblages were altogether absent or were 

 present in reduced abundances in canyons. However, later 

 work by Haedrich, Rowe and Polloni (19 75) based on the results 

 of 29 trawls, demonstrated that even though canyon fauna was 

 not noticably different from slope fauna several species 

 could be recognized as being "canyon indicators". 



The results of the historical survey show that canyon 

 habitats differ significantly from slope habitats, and that 

 the previous comparisons of slope and canyon epifauna do not 

 adequately reflect the faunal constituency of large canyon 

 systems (Appendix A) . With regard to faunal assemblages 

 canyons are particularly interesting in that they provide a 

 heterogeneous environment, characterized by a variety of 

 available substrate types, when compared to similar depths on 

 the slope. The distribution of some species of epifauna is 

 largely determined by the availability of suitable substrate 

 (Hecker et al. , 1978). As a result canyon assemblages differ 

 from slope assemblages by being composed of a greater variety 

 of trophic types. The most notable trophic type found in 

 higher concentrations in canyons than on the continental slope 

 are filter- feeders. They are usually sessile and many are 

 restricted to the hard substrates, such as outcrops, boulders 

 and talus blocks, that are common in deeply incised canyons. 



