740 



Fishery Bulletin 100(4) 



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Figure 1 



Location of Heceta Bank and the adjacent continental margin in relation to the Oregon coast. The 

 survey area is outlined in bold lines. 



al.. 2000; Hixon et al."*; Hixon and Tissot''). Correlations 

 over larger regions have been difficult to determine be- 

 cause of the limitations in the resolution and areal cover- 

 age of bathymetric charts, which are crucial in providing 

 broad-scale habitat data. However, this difficulty no longer 

 exists with the advent of differential GPS and high-reso- 

 lution sonar systems (Hughes Clarke et al., 1996). When 

 adequately groundtruthed. these new systems provide 

 bathymetric and backscatter data with sufficient resolu- 

 tion to formulate habitat classifications over broad areas 

 of the continental shelf and slope (Able et al.. 1987; Yokla- 

 vich et al., 1995; Greene et al.'^ Fox et al."). 



^ Hixon. M. A., B. N. Tissot. and W. G. Pearcy. 1991. Fish 

 assemblages of rocky banks of the Pacific northwest. Final 

 report. OCS Study MMS 91-0052. 410 p. USDI I\hnerals Man- 

 agement Service, 770 Pasea, Camarillo, CA 93010. 



' Hixon. M. A., and B. N. Tissot. 1992. Fish assemblages of 

 rocky banks of the Pacific northwest. Final report supplement, 

 OCS Study MMS 92-002.5. 128 p. USDI Mineral Management 

 Service. 770 Pasea. Camarillo, CA 93010, 



' Greene, H. G., M. M. Yoklavich, D. Sullivan, and G. CailUet, 

 1995. A geophysical approach to classifying marine benthic 

 habitats: Monterey Bay as a model. Alaska Department of Fish 

 and Game Special Publ. 9, p. 15-30. Alaska Department of 

 Fish and Game, PO. Box 25526. Juneau, AK 99802. 



We developed this habitat-based groundfish assess- 

 ment strategy by integrating a comprehensive submers- 

 ible survey with new high-resolution sonar imagery of 

 the seafloor Sonar images produce habitat data by using 

 acoustic signals to differentiate areas of hard substrata 

 from surrounding soft sediments based on differences in 

 the intensity of reflected sound. This technology has the 

 distinct advantage of examining large regions of seafloor 

 sediment and geological topographic features without 

 relying on expensive direct underwater bottom sampling 

 and observation techniques. Sonar data can be used in an 

 assessment of seafloor habitat and fish density over large 

 areas by extrapolating from direct observations offish and 

 seafloor morphology transects using manned submers- 

 ibles or remotely operated vehicles. 



The study site for this assessment was Heceta Bank, a 

 SO-km long outcrop on the outer shelf of central Oregon 

 (Fig. 1). Heceta Bank is the largest rocky reef of the Pa- 

 cific Northwest and is characterized by high variability 

 in bottom types and textures. The bank provides a diver- 

 sity of habitat types for many species of groundfish and 



Fox, D., M. Amend, and A. Merems. 1999. Nearshore rocky 

 reef assessment. Coastal Management Section 309 Grant. 

 Contract No. 99-072. Oregon Department of Fish and Wildlife, 

 2040 SE Manne Science Drive. Newport. OR 97365 



