178 



Fishery Bulletin 105(2) 



that for R. nicholsii sediment gaps within or adjacent 

 to a rocky landscape were required. 



On the other hand, S. chlorostictus and S. elongatus 

 were both more abundant in the mixed stratum than 

 in the hard stratum (broad scale) and were present 

 together within mixed boulder, cobble, and mud sub- 

 strata (intermediate scale). At fine scales, however, 

 microhabitat use by these species differed; S. elongatus 

 was common in the mud portion of these patches and 

 S. chlorostictus was common over boulders and cobbles. 

 These findings indicated that both species were in- 

 terface associates, but within these interface regions 

 different substratum types were used. The inclusion 

 of microhabitat information within this multiscale ap- 

 proach provided a more comprehensive understanding 

 of how demersal fish use benthic substrata. However, 

 recording microhabitat use for each fish (« =21,184 

 fishes) was time consuming and therefore would likely 

 negate its use in some studies. A recommended alter- 

 native method for recording microhabitat use might 

 be to measure microhabitat use for a subset of fish per 

 species, where subsamples are selected unbiasedly from 

 the overall sample pool. 



The ability to describe and predict fish-habitat re- 

 lationships, as identified in this study, can be used to 

 address area-based management concerns in several 

 ways. For example, species captured by benthic trawl 

 and long-line gear could be used to infer the presence 

 of seafloor substratum types. Although this form of 

 information is not novel, our study provides detailed 

 quantitative species-habitat associations that validate 

 this approach. For example, a benthic trawl that cap- 

 tures Pleuronectidae, Agonidae, S. semicinctus, S. chlo- 

 rostictus, and S. elongatus, would indicate that the area 

 trawled encompassed multiple strata (e.g., one or more 

 areas of low-relief outcrop and homogenous mud). How- 

 ever, the proportions and spatial configuration of these 

 strata would not be known unless a video camera, for 

 example, was mounted on a benthic trawl (e.g., Abookire 

 and Rose, 2005), or a seafloor substrata map was avail- 

 able for the area (e.g.. Bellman et al., 2005). 



Conversely, habitat could be used to predict commu- 

 nity structure and species distributions. In this study, 

 substratum type was a good indicator of distribution 

 and abundance of many commercial and noncommer- 

 cial fish species. However, the spatial arrangement and 

 degree of habitat patchiness, in addition to substra- 

 tum type, also were important predictive variables. 

 Consequently, although areal estimates of substrata 

 are likely to be effective for modeling the abundance 

 and distribution of certain species (e.g., S. rosaceus 

 and S. flavidus), accurately estimating other species 

 will require additional knowledge of the spatial ar- 

 rangement of these substrata. For example, species 

 associated with sediment-rock interfaces, such as S. 

 chlorostictus, S. elongatus, and Z. frenata, are likely to 

 be modeled more effectively by estimating the perimeter 

 of either an outcrop or specific habitat type. Likewise, 

 the ability to model gap-associate species, such as R. 

 nicholsii, will require information on the availability of 



sediment-outcrop interfaces and sediment gaps within 

 an outcrop matrix. For other species, such as young- 

 of-year rockfish, a measure of habitat patchiness, in 

 combination with areal estimates of substrata, may be 

 required. The ability to map this level of habitat detail 

 will depend to a large degree on a trade-off between 

 data acquisition and resolution of the mapping tools 

 used, and the amount of seafloor needed to be mapped 

 (Anderson et al., 2005). 



In conclusion, the overall success of area-based man- 

 agement strategies will reflect the ability of research- 

 ers to accurately measure the functional relationships 

 between organisms and their habitat. Multiscale in 

 situ surveys, such as this one, undertaken in multi- 

 ple locations, in combination with larger-scale fishery 

 surveys can improve our understanding of the role of 

 benthic habitats in structuring demersal fishes across 

 the broader U. S. West Coast. These insights, in turn, 

 improve our ability to characterize and map essential 

 fish habitat, estimate habitat availability, and predict 

 multispecies distributions and habitat associations 

 within specified areas such as marine protected areas. 

 Importantly, this study also provides a quantitative 

 baseline of demersal fish assemblage structure for both 

 commercial and noncommercial species, which is critical 

 for future comparisons of spatiotemporal abundance, 

 diversity, and habitat use. This baseline is also vital for 

 assessing the effects and value of increased protection 

 of West Coast shelf ecosystems. 



Acknowledgments 



We thank G. Cailliet, R. Lea, M. Love, G. Moreno, 

 R. Parrish, P. Reilly, L. Snook, R. Starr, D. Sullivan, 

 the Delta Oceanographies (R. Slater, D. Slater, and C. 

 Ijames) for logistical support and biological data collec- 

 tion. We thank M. Carr, C. Grimes, S. Ralston, C. Syms, 

 B. Tissot, and W. Wakefield for their conversations and 

 advice during the analysis and writing of this research, 

 and Tim Simmonds and Guy Cochrane for graphical 

 support. The manuscript was improved through the com- 

 ments of M. Cappo, C. Grimes, T. Laidig, C. Syms, and 

 three anonymous reviewers. This project was partially 

 supported by NOAAs National Undersea Research Pro- 

 gram, West Coast and Polar Undersea Research Center, 

 University of Alaska, Fairbanks (Grants UAF-92-0063 

 and UAF-93-0036) and by a University of California, 

 Santa Cruz postdoctoral fellowship to Tara Anderson, 

 with joint funding from National Marine Fisheries Ser- 

 vice, U. S. Geological Survey, and the National Marine 

 Protected Areas Center Science Institute. 



Literature cited 



Abookire, A. A., and C. S. Rose. 



200.5. Modifications to a plumb staff beam trawl for 

 sampling uneven, complex habitats. Fish. Res. 71: 

 247-254. 



