625 



Abstract.— A multidiseiplinary assess- 

 ment of benthic rockfishes (genus Se- 

 bastes) and associated habitats in deep 

 water was conducted in Soquel Sub- 

 marine Canyon, Monterey Bay, Califor- 

 nia. Rock habitats at depths to 300 m 

 were identified by using bathymetric 

 and side-scan sonar imaging, verified by 

 visual observations from a manned sub- 

 mersible, mapped and quantified. Spe- 

 cies composition, abundance, size, and 

 habitat specificity of fishes were deter- 

 mined by using a video camera and par- 

 allel laser system along transects made 

 by a submersible. 



We counted 6208 nonschooling fishes 

 representing at least 52 species from 83 

 10-min strip transects that covered an 

 estimated 33,754 m-. Rockfishes repre- 

 sented llVc of the total number of indi- 

 viduals, and included a minimum of 24 

 species. Six distinct habitat guilds of 

 fishes were manifest from habitat-based 

 clustering analysis: small species were 

 associated with mud and cobble sub- 

 strata of low relief, and larger species 

 of rockfishes were associated with high- 

 relief structures such as vertical rock 

 walls, ridges, and boulder fields. There 

 was remarkable concordance between 

 some of the guilds identified in Soquel 

 Canyon and the results of other habi- 

 tat-specific assessments of fishes along 

 the west coast of the United States 

 from central California to Alaska. These 

 generalities are valuable in predicting 

 community structure and evaluating 

 changes to that structure, as well as 

 in applying small-scale species-habitat 

 relationships to broader-scale fishery 

 resource surveys. Additionally, estab- 

 lishment of these groups is critical when 

 incorporating the concept of essential 

 fish habitat ( EFH ), and negative impacts 

 to it, into the management of fisheries 

 in relatively deep water, as required by 

 the Sustainable Fisheries Act of 1996. 



High numbers of large rockfishes (e.g. 

 Sebastes chlorostictus.S. levis.S. rvsenb- 

 blatti. and S. rubernmus^ were locally 

 associated with rock ledges, caves, and 

 overhangs at sites having little or no 

 evidence of fishing activity. Abundance 

 and size of several species were lower 

 at fished than at unfished sites. We sug- 

 gest that rock outcrops of high relief 

 interspersed with mud in deep water 

 of narrow submarine canyons are less 

 accessible to fishing activities and 

 thereby can provide natural refuge for 

 economically important fishes, as exem- 

 plified in Soquel Canyon. 



Manuscript accepted 17 December 1999. 

 Fish. Bull. 98:625-641 (2000i. 



Habitat associations of deep-water rockfishes 

 in a submarine canyon: an example of 

 a natural refuge 



Mary M. Yoklavich 



Pacific Fisheries Environmental Laboratory 



National Marine Fisheries Seivice, NOAA 



1352 Lighthouse Avenue 



Pacific Grove, California 93950-2097 



Present address: National Manne Fisheries Service 

 "■/o Long Marine Laboratory 

 100 Shaffer Road 

 Santa Cruz, California 95060 



E-mail address maryyoklavichgnoaagov 



H. Gary Greene 



Gregor M. Cailliet 



Deidre E. Sullivan 



Moss Landing Marine Laboratories 



8272 Moss Landing Road 



Moss Landing, California 95039-9647 



Robert N. Lea 



California Department of Fish and Game 

 20 Lower Ragsdale Dr 

 Monterey, California 93940 



Milton S. Love 



University of California Santa Barbara 

 Manne Science Institute 

 Santa Barbara, California 93106 



Rockfishes iSebastes spp. ) are quite 

 speciose, (dominate coastal benthic fish 

 assemblages on the west coast of the 

 United States, and are among the most 

 valuable fisheries in California. They 

 have been harvested commercially in 

 California as early as 1875 (Phillips, 

 1957). About 859c of the 57 or more 

 rockfish species in California have some 

 economic value, and landings have 

 increased dramatically over the last 

 40 years (Lea, 1992). During the past 

 decade (1988-97), commercial fisher- 

 men have landed an average of nearly 

 10,000 metric tons of rockfish at Cali- 

 fornia ports per year, with an average 

 exvessel value of $11.4 million per year 

 (Thomson, 1999). During this period, 

 recreational anglers on commercial pas- 

 senger fishing vessels caught an addi- 

 tional 1,8 million individual rockfish 

 per year (Thomson, 1999), at a value 



that far exceeds that of the commercial 

 catch. 



Many species of rockfishes are slow- 

 growing, long-lived, and relatively old 

 at maturity, making them particularly 

 vulnerable to overfishing. Historically, 

 rockfish landings have been especially 

 high in Monterey (Phillips, 1939), and 

 there are recent indications that num- 

 bers and sizes are decreasing for some 

 species (Pearson and Ralston, 1990; 

 Mason, 1995, 1998; Ralston, 1998). As 

 with many coastal fisheries, the Mon- 

 terey fleets have expanded their range 

 to deeper and more remote areas as 

 local stocks have become depleted in 

 shallow water ( Deimling and Liss, 1994; 

 Karpov et al., 1995; Mason, 1995). 



As increased fishing effort is applied 

 to populations in deep coastal waters, 

 it becomes critical to identify and pro- 

 tect areas of natural refuge for larger. 



