Abstract. - Heceta Bank is a 

 large reef on the edge of the central 

 Oregon continental shelf that sup- 

 ports a wide variety of commercial 

 fisheries. Using the research sub- 

 mersible Delta, we studied fish abun- 

 dances on Heceta Bank and the rela- 

 tionship between species composition 

 of fish assemblages and bottom 

 types. Cluster analysis indicated that 

 fish assemblages were most unique 

 on mud, boulder, rock ridge, mud 

 and cobble, and mud and boulder 

 substrates. Rockfishes, particularly 

 pygmy Sebastes vnlsoni, sharpchin S. 

 zacentrus, rosethom S. helvomacula- 

 tus, and yellowtail S.flavidus, were 

 the most abundant fishes and dom- 

 inated all substrates except mud, 

 where Dover sole Microstomics paci- 

 ficus and zoarcids Lycodes pacificus 

 were most abundant. 



Principal component analysis 

 (PCA) and canonical correlation anal- 

 ysis (CCA) were used to determine 

 the sources of variation within the 

 data. PCA demonstrated that habi- 

 tat variability was a fundamental 

 cause of heterogeneity among fish 

 assemblages. In contrast, CCA 

 showed how species occurrences 

 were related to specific substrates. 



Ontogenetic shifts in behavior and 

 substrate preference occurred in 

 pygmy rockfish. Small juveniles 

 often formed dense schools above the 

 bank's shallower rocky ridges. 

 Larger individuals occurred in non- 

 polarized assemblages on the bottom 

 in cobble and boulder fields. 



Fish-habitat associations on a 

 deep reef at the edge of the 

 Oregon continental shelf 



David L. Stein 



Department of Oceanography, Oregon State University, Corvallis, Oregon 9733 1 -29 1 4 



Brian N. Tissot 



Department of Zoology, Oregon State University, Corvallis, Oregon 97331-2914 

 Present address: Department of Biology, College of Arts and Sciences 

 University of Hawaii, Hilo, Hawaii 96720 



Marl< A. Hixon 



Departments of Oceanographiy and Zoology, Oregon State University 

 Corvallis, Oregon 97331-2914 



William Barss 



Oregon Department of Fish and Wildlife. Newport, Oregon 97365 



Manuscript accepted 11 May 1992. 

 Fishery Bulletin, U.S. 90:540-551 (1992). 



Heceta Bank is a major commercial 

 fishery zone off central Oregon. It 

 supports a wide variety of fisheries: 

 a demersal trawl fishery for many 

 species of flatfishes; a longline fish- 

 ery for halibut Hippoglossus stenole- 

 pis; midwater trawl and vertical long- 

 line fisheries for rockfishes (Sebastes 

 spp.); a midwater trawl fishery for 

 hake Merluccius productus; and dur- 

 ing upwelling, a troll fishery for 

 salmon (Oncorhynchus spp). Despite 

 its importance to commercial fisher- 

 ies, little was known about Heceta 

 Bank prior to our 1987 submersible 

 studies (Pearcy et al. 1989). From 

 those exploratory dives we learned 

 that (1) the bank is composed of 

 diverse substrates, each supporting 

 fish assemblages differing in species 

 composition and relative abimdances; 



(2) shallow areas of the bank act as 

 a nursery for juvenile rockfishes; and 



(3) commercially valuable species of 

 rockfish are associated with the shal- 

 low bank top in untrawlable areas, 

 which thus serve as refugia from 

 most commercial fishing. 



Our 1987 studies focused on initial 

 exploration and description of the 

 Bank. Here we report results from 



our 1988 submersible-based surveys 

 in which we again studied the fishes 

 occurring on the Bank, concentrating 

 specifically on their associations with 

 various bottom types. We selected 

 sampling stations that represented 

 the range of habitats described by 

 Pearcy et al. (1989) (Fig. 1). Our ob- 

 jectives were to (1) further develop 

 methods of collecting and analyzing 

 data that could be gathered from a 

 submersible to study rocky banks; 

 (2) identify the species occurring on 

 Heceta Bank and estimate their rela- 

 tive and absolute abundances; (3) 

 obtain detailed information about the 

 variability of bottom types occurring 

 within each station; and (4) assess the 

 composition of fish assemblages in 

 relation to different bottom types. 



Methods 



Data collection 



We used the submersible Delta to 

 make 18 dives at six stations on 

 Heceta Bank in September 1988 

 (Fig. 1). These stations represented 

 all substrates and depths within 

 range of the submersible (to 366 m). 



540 



