854 



Fishery Bulletin 100(4) 



Table 5 



Suggested species assemblages based on distribution, ordi- 

 nation, and partitioning analyses completed in this study. 



Habitat 



Species 



Deepwater slope blackgill rockfish, aurora rockfish, 



shortspine thomyhead, bank rockfish, 

 darkblotched rockfish. Pacific ocean 

 perch, redbanded rockfish, 

 splitnose rockfish 



Nearshore copper rockfish, vermilion rockfish. 



brown rockfish, halfbanded rockfish 



Southern shelf chilipepper, shortbelly rockfish, 



bocaccio, stripetail rockfish, 

 greenstriped rockfish, greenspotted 

 rockfish, cowcod 



Northern shelf canary rockfish, ycUowtail rockfish, 



widow rockfish, sharpchin rockfish, 

 rosethorn rockfish, yelloweye rockfish, 

 redstripe rockfish 



leaving the 200-250 m zone as an area of overlap for the 

 two assemblages, which is exactly where the peak in rich- 

 ness occurred. The species in the nearshore assemblage 

 seem to reside in waters less than 150 m depth. Perhaps 

 the 100-150 m zone represents an area of overlap between 

 the shelf and nearshore species. 



Latitudinal divisions between species in the northern 

 and southern shelf assemblages are not as well defined as 

 those based on depth. It appears that most of the southern 

 shelf group are uncommon above the Mendocino Escarp- 

 ment ( 40.8°N latitude ), with the exception of stripetail and 

 greenspotted rockfish. The northern shelf species tend to 

 range as far south as Monterey Canyon, leaving the area 

 between Monterey Canyon and the Mendocino Escarp- 

 ment as an area of overlap for these assemblages. This 

 overlap is confirmed in the species richness contour plot 

 which indicates the areas where the highest number of 

 species were found in that latitude zone (Fig. 5i. The only 

 questionable assemblage assignment was the placement 

 of greenstriped rockfish, which does not range south of the 

 Monterey Canyon region but whose center of its distribu- 

 tion was observed in the 38.0°N latitude area. 



Overall, the results of our study indicate that rockfish 

 can be classified into fairly distinct assemblages based on 

 their depth and latitude distributions. This study also pro- 

 vides estimates of the co-occurrence in the form of overlap 

 measures for the important rockfish species off the coast of 

 California. Both the assemblage and co-occurrence infor- 

 mation should prove useful to fishery managers for model- 

 ing fishery dynamics, solving bycatch issues, establishing 

 area closures, and determining effective marine reserves. 

 Although our study highlights some uses of spatial infor- 

 mation, the limited amount of data that is now available 

 prevents a more thorough analysis of interannual vari- 

 ability in the distribution of species. We would therefore 



like to stress the importance of collecting more informa- 

 tion describing the spatial distribution and co-occurrence 

 of catches and the usefulness of those data in developing 

 new strategies for managing west coast rockfish fisheries. 



Acknowledgments 



We gratefully acknowledge the assistance of Mark Wil- 

 kins, who instructed us on how to properly access and 

 interpret RACEBASE, the Alaska Fisheries Science Cen- 

 ter's relational data base in which the triennial continen- 

 tal shelf trawl survey data are stored. We also wish to 

 thank Alec MacCall, Rick Methot, Ken Weinberg, and 

 Mark Wilkins for their reviews of an early version of this 

 manuscript. 



Literature cited 



Bloom, S. A. 



1981. Similarity indices in community studies: potential 

 pitfalls. Mar. Ecol. Prog. Ser. 5:125-U128. 



Chen, L. C. 



1986. Meristic variation in Sebastes (Scorpaenidae), with 

 an analysis of character association and bilateral pattern 

 and their significance in species separation. U.S. Dep. 

 Commer., NOAA Tech. Rep. NMFS 4.5, 17 p. 

 Chess, J. R., S. E. Smith, and P C. Fischer. 



1988. Trophic relationships of the shortbelly rockfish, 

 Sebastes jordani, off central California. CalCOFI Rep. 

 29:129-136. 

 Dark, T. A., and M. E. Wilkins. 



1994. Distribution, abundance, and biological characteris- 

 tics of groundfish off Washington, Oregon, and California, 

 1977-1986. U.S. Dep. Commer., NOAA Tech. Rep. NMFS 

 117, 73 p. 

 Eschmeyer, W. N. (ed.). 



1998. Catalogoffishes, 2905 p. California Academy of Sci- 

 ences, San Francisco, CA. 

 Eschmeyer, W. N., E. S. Herald, and H. Hammann. 



1983. A field guide to Pacific coast fishes, 336 p. Houghton 

 Mifflin Company, Boston, MA. 

 Field. J. G., K. R. Clarke, and R. M. Wamick. 



1982. A practical strategy for analyzing multispecies distri- 

 bution patterns. Mar Ecol. Prog. Ser. 8:37-52. 



Fox, D. S., and R. M. Starr. 



1996. Comparison of commercial fishery and research catch 

 data. Can. J. Fish. Aquat. Sci. 53:2681-2694. 



Fujita, R. M., T. Foran, and I. Zevos. 



1998. Innovative approaches for fostering conservation in 

 marine fisheries. Ecol. Appl. 8(1):S139-S150. 

 Gabriel, W. L., and A. V. Tyler 



1980. Preliminary analysis of Pacific coast demersal fish 

 assemblages. Mar. Fish. Rev 42(3-41:83-88. 

 Gunderson, D. R. 



1997. Spatial patterns in the dynamics of slope rockfish 

 stocks and their implications for management. Fish. Bull. 

 95:219-230. 



Hartigan, J. A., and M. A. Wong. 



1979. A *-means clustering algorithm. Appl. Stat. 28: 100- 

 108. 

 Jay, C. V. 



1996. Distribution ofbottom-trawl fish assemblages over the 



