substrate. Substrate was either fine sandy mud, characteristic 

 of the continental shelf edge off Oregon, or rock ( CaCO~ ). Four 

 substrate categories were designated for analysis of 

 invertebrates and fishes to determine if the presence of hard 

 substrate affects composition of shelf benthos; these were: 

 (1) mud, (2) mud near rock, (3) rock near mud, and (4) rock. 



Caution is necessary in considering the "all mud" category, 

 because rock could have been present just beyond the photograph. 

 Because photographic coverage was not evenly distributed, numbers 

 of observations do not indicate frequency of occurrence and are, 

 therefore, not included. Because quantitative transects were not 

 made, these data represent only presence or absence of fish and 

 invertebrate taxa (identified to lowest possible taxon) in still 

 photographs taken at varying altitudes and spatial intervals. 



In 1987, we also utilized a remotely operated vehicle ( ROV 

 Recon-IV) for surveys of the chimney field. Also in 1987, animal 

 and rock collections were made with the submersible manipulator 

 arms and a 7.1 m otter trawl with 1.3 cm mesh towed from R/V 

 Aloha at 1.5 to 2.0 knots. 



RESULTS 



The invertebrates living on the sediments of Nehalem Bank 

 are similar to those in other regions of the Oregon continental 

 slope and outer shelf (Appendix 1). Many of the same species of 

 asteroids, holothuroids, and echinoids were present. Echinoids, 

 Allocentrotus f ragilis and Brisaster townsendi , are common in the 

 Nehalem Bank sedimentary environment; the holothuroid 

 Parastichopus californicus occurs on the sediment surface in low 

 abundance. B_^ latif rons is a burrowing sea urchin that can be 

 observed breaking the sediment surface, leaving characteristic 

 wide, meandering burrow patterns. Ophiuroids are abundant in 

 some areas. We observed an alcyonarian ( Anthomastus ritteri ?) 

 never collected by us with conventional sampling gear that, in 

 Oregon waters, may be restricted to rocky environments. 

 Rockfishes (family Scorpaenidae ) were observed throughout the 

 area (Table 1). 



The fauna collected from the rocky substrate was noticeably 

 different from our previous collections from the Oregon shelf 

 edge, probably an indication of the difficulty of trawling in 

 this rugged environment during past research projects. Typical- 

 ly, commatulid crinoids, psolid holothuroids, chitons, ophiu- 

 roids, brachiopods, corals, sponges, actiniarians and other hard 

 substrate epifauna cover the surface of calcium carbonate slabs 

 and chimneys (Table 2). Occasionally, predaceous starfish, such 

 as Luidea foliolate and Pisaster sp. , occur on the rock 

 surfaces. One large actiniarian inhabiting the rocky substrate 

 is new, to our knowledge, off Oregon; it resembles a white sphere 



141 



