Submersible Observations of Deep-Reef Fishes of 

 Heceta Bank, Oregon 



W. G. Pearcy, D. L. Stein, M. A. Hixon, E. K. Pikitch, 

 W. H. Barss, and R. M. Starr 



ABSTRACT: Rockfishes, Sebastes spp., were the 

 most numerous and speciose fishes seen during 16 

 submersible dives from 64 to 305 m depth in the 

 vicinity of Heceta Bank off the coast of Oregon. 

 Dense schools of juvenile rockfishes and large yel- 

 lowtail rockfish, S. flavidus, were observed only 

 over rocky, high relief areas near the top of the 

 bank, and highest densities of small benthic rock- 

 fishes (up to 5-10/m') on the flanks of the bank. 

 These observations suggest that shallow, rocky 

 portions of Heceta Bank are a nursery area for juve- 

 nile rockfishes. Two species groups of nonschool- 

 ing fishes were identified based on transects over 

 the diverse seafloor habitats around the bank: one 

 comprised primarily of rockfishes in shallow water 

 on rock and cobble, and the other comprised of 

 flatfishes, agonids, sablefish, and some rockfishes 

 in deep water over mud and cobble. Species compo- 

 sition of fishes observed from submersible dives dif- 

 fered from species composition of fishes taken from 

 trawl catches in the same general areas. 



Prominent offshore submarine banks of exposed 

 bedrock, formed by subduction of oceanic plates, 

 occur along the continental shelf of western 

 North America (Kulm and Fowler 1974), provid- 

 ing a specialized habitat for marine fauna. Large 

 aggregations of rockfishes (Scorpaenidae: 

 Sebastes) and other fishes are often associated 

 with these banks (Isaacs and Schwartzlose 

 1965), just as concentrations of fishes are found 

 on or over seamounts in the North Pacific Ocean 

 (Uda and Ishino 1958; Uchida and Tagami 1985; 

 Uchida et al. 1986). 



Heceta Bank, located about 55 km off the cen- 

 tral Oregon coast, rises abruptly from depths of 



W. G. Pearcy and D. L. Stein, College of Oceanography, 



Oregon State University, Corvallis, OR 97331. 



M. A. Hixon, College of Oceanography and Department of 



Zoology, Oregon State University, Corvallis, OR 97331. 



E. K. Pikitch, Department of Fisheries and Wildlife, Oregon 



State University, Corvallis, OR 97331; present address: 



Fisheries Research Institute, University of Washington, 



Seattle, WA 98195. 



W. H. Barss and R. M. Starr, Oregon Department of Fish 



and Wildlife, Hatfield Marine Science Center, Newport, 



OR 97365. 



Manuscript accepted February 1989. 

 Fishery Bulletin, U.S. 87:955-965. 



over 1,000 m on its seaward face to depths of 

 <60 m (Figs. 1, 2). Trawlable areas around 

 Heceta Bank support a large portion of Oregon's 

 commercial fishery production. The bank itself is 

 thought to be a nursery for juvenile fishes. Sev- 

 eral surveys of near-bottom fishery resources of 

 the region have been attempted using bottom 

 trawls (Gunderson and Sample 1980; Barss et al. 

 1982; Weinberg et al. 1984). However much of 

 the bank is too rugged for bottom trawling, and 

 until our study, no submersible surveys of this 

 area had been made. Thus, species composition, 

 abundances, and distributions of fishes on 

 Heceta Bank itself are largely unknown. 



We used a manned submersible to conduct sur- 

 veys of fishes on and around Heceta Bank. Our 

 goals were to assess visually the abundances of 

 fishes on Heceta Bank, to relate distributions 

 and species assemblages with habitat type and 

 depth, and to evaluate the impoilance of the 

 bank as a nursery and refugium for commercially 

 important fishes. 



METHODS 



We dove 16 times in the vicinity of Heceta 

 Bank (Fig. 2) during daylight on 23-31 August 

 1987, using the submersible Mermaid II. Bot- 

 tom depths ranged from 64 to 305 m. Usually 

 two or three visual belt transects were made 

 during each dive. During each transect the posi- 

 tion of the submersible and the distance tra- 

 versed in 30 minutes at speeds of 1.5-2.0 km/h 

 were determined from Loran C fixes by the sur- 

 face vessel Aloha as it followed a surface buoy 

 towed by the submei'sible. In this paper we re- 

 port on 21 transects from 10 dives in which the 

 submersible attempted to follow a compass 

 course parallel to isobaths. Two scientists and a 

 pilot were on each dive. Scientists switched posi- 

 tions from the bow window to a stern jump seat 

 between 30 min transects. Seven scientists made 

 dives. 



All fishes seen between two fixed points on the 

 submersible's bumper (a path about 3.5 m wide 



955 



