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Fishery Bulletin 97(4), 1999 



X/1^ 



Figure 1 



Perspective, shaded-relief view of the study area based on high-resolution multibeam bathymetry. Vertical exaggeration is 20-. The 

 continental shelf (< 120 m water depth) is bathymetrically smooth owing to large input of fine terrigenous sediments from the Eel and 

 Mad Rivers and to reworking by storms. The southern portion of the shelf is dominated by the Humboldt slide. The northern portion of 

 the slope is -60 m deeper and ~7 km farther from shore than in the Humboldt slide area. 



rigged with a 33.5-m { 110-ft) net opening with trawl 

 doors hung -76-91 m (250-300 ft) apart. 



The trawl fishery on the shelf primarily occurs over 

 soft-sediment habitat and mainly targets flatfishes. 

 The important species in this assemblage include 

 English sole (Pleuronectes vetulus), Petrale sole 

 (Eopsetta jordani), and sanddabs iCitharichthys 

 spp. ). The slope fishery occurs over rougher and more 

 heterogeneous habitats that begin at the shelf break 

 (-120 m) and continue to depths >900 m. The catch 

 in this assemblage is dominated by Dover sole (Mi- 

 crostomus pacificus), sablefish (Anoplopoma fimbria ), 

 thornyheads (Sebastolobus spp.), and several rock- 

 fish species (Sebastes spp.). A midwater trawl fish- 

 ery also exists in waters above the slope for Pacific 

 whiting (Merliiccius productiis) and widow rockfish 

 {Sebastes entomelas). The assemblages in this region 

 are similar to those found along other portions of the 

 U.S. west coast by the National Marine Fisheries 

 Service triennial trawl surveys (Jay, 1996). 



Groundfish are among the most diverse and eco- 

 nomically valuable fishery resources along the west 



coast of the United States (NOAA, 1996). Diversity, 

 quality, and extent of habitat are among the most 

 important environmental determinants of distribu- 

 tion, abundance, and species diversity for ground- 

 fish (Carlson and Straty, 1981; Matthews and 

 Richards, 1991). The broad spatial extent of these 

 fisheries generally precludes careful examination of 

 the nature of the exploited habitats, the relationship 

 among species and habitats, and the degree to which 

 fishing activities have affected these habitats. Con- 

 servation of fisheries habitat is an important con- 

 sideration for sustaining fisheries production. The 

 reauthorization of the Magnuson-Stevens Fisheries 

 Conservation and Management Act requires incor- 

 porating the concept of "essential fish habitat" in 

 Fishery Management Plans (Schmitten, 1996). Be- 

 cause fishing, particularly with bottom trawls, can 

 alter essential fish habitat, it is important to quan- 

 tify fishing activity and its effects on the associated 

 habitat. The goals of this study are to evaluate the 

 extent of marks from bottom trawls off Eureka, Cali- 

 fornia, at a scale consistent with commercial fishing 



