1 13 



AbStraCt.-Submersible belt-tran- 

 sect surveys along a rocky bottom were 

 combined with acoustic surveys of the 

 water column to estimate depth distri- 

 bution and density of fishes at Stone- 

 wall Bank, Oregon, in the northeast- 

 ern Pacific Ocean from September 

 through October 1991. The objectives 

 of the study were to determine the pro- 

 portion offish in the water column that 

 were not detected by submersible sur- 

 vey techniques and to compare esti- 

 mates of fish density near the bottom 

 from submersible surveys with density 

 estimates from hydroacoustic surveys. 

 More than 75% of the fishes recorded 

 on acoustic surveys resided in the bot- 

 tom third of the water column. Rock- 

 fishes (family Scorpaenidae) were the 

 predominate fish taxa observed in the 

 study area. Estimates of fish density 

 from submersible surveys were more 

 than six times greater than estimates 

 of fish density near the bottom from 

 hydroacoustic surveys. Submersible 

 and acoustic surveys provided different, 

 but complementary, information re- 

 garding the use of rocky banks by fish. 

 Submersible surveys provided esti- 

 mates of fish density near the bottom 

 and provided valuable ground-truth for 

 acoustic equipment. Hydroacoustic sur- 

 veys provided estimates offish density 

 in the portions of the water column not 

 observed on submersible transects and 

 provided additional information on the 

 vertical and horizontal distribution of 

 fishes. The combined use of submers- 

 ible and acoustic sampling techniques 

 provided a better understanding of how 

 fish use rocky banks than did either 

 technique alone. 



Comparison of submersible-survey 

 and hydroacoustic-survey estimates 

 of fish density on a rocky bank 



Richard M. Starr* 



Sea Grant Extension Program, University of California 

 Box 440, Moss Landing, California 95039 



David S. Fox 



Oregon Department of Fish and Wildlife 



SE Marine Science Dr. Newport, Oregon 97365 



Mark A. Hixon 



Department of Zoology, Oregon State University 

 Corvallis. Oregon 9733 I -29 1 4 



Brian N. Tissot 



Marine Science Department, University of Hawaii at Hilo 

 W Kawili St., Hilo. Hawaii 96720 



Gary E. Johnson 



Bonneville Power Administration 



RO Box 3621, Portland, Oregon 97208 



William H. Barss 



Oregon Department of Fish and Wildlife 



SE Marine Science Dr., Newport, Oregon 97365 



Manuscript accepted 14 July 1995. 

 Fishery Bulletin 94:113-123 (19961. 



Large aggregations of fishes are 

 associated with rocky banks along 

 the Pacific coast of North America. 

 Many of these banks are located 

 along the edge of the continental 

 shelf and provide important habi- 

 tat for commercially and recrea- 

 tionally valuable species (Carlson 

 and Straty, 1981; Nagtegaal, 1983; 

 Pearcy et al., 1989). Fishes har- 

 vested from the rocky banks are of- 

 ten associated with bottom habitats, 

 especially fishes in the family 

 Scorpaenidae (rockfishes and their 

 relatives). 



Assessment of the distribution 

 and relative abundance of these 

 bottom dwelling fishes is difficult 

 because of the limitations of exist- 



ing field-sampling techniques. Bot- 

 tom trawls have been used to assess 

 fishery resources over the continen- 

 tal shelf and along the edge of some 

 offshore rocky banks since the 

 1970's (Gunderson and Sample, 

 1980; Leaman and Nagtegaal, 1982; 

 Dark et al., 1983; Weinberg et al., 

 1984), but rugged topography has 

 precluded the use of trawls for as- 

 sessing fishes on the tops of the 

 banks. Trawls are also a poor tool 

 for sampling rocky areas (Carlson 

 and Straty, 1981; Butler et al., 

 1991). A few researchers have suc- 

 cessfully sampled rocky areas using 



Affiliated with University of California, 

 Davis. CA 95616. 



