630 



Fishery Bulletin 98(3) 



evenly distributed (see results of diversity analysis that 

 follows), and included mostly small species (i.e. S. semi- 

 cinctus, S. wilsoni, and S. elongatus) and small members 



A rO 



o 

 o 



0) 



■g 

 CO 



m 



-180 m- 



300 m 



nOm 



"D 



"-120m-' 



300 m 





Figure 3 



lAl Side-scan monograph of isolated rock outcrop on steep wall of 

 Sequel Canyon. Strong acoustic reflectors (dark areas) are from 

 exposed bedding faces, white areas are shadows behind faces, 

 and gray areas are nonreflective mud. (B) These eroded mud- 

 stone beds comprise habitat for benthic fishes, such as this adult 

 grecnspotted rockfish LSchcistet: fhloroslicliix). IC) Side-scan sono- 

 graph of steep, well-bedded rock walls on southeast side of canyon 

 from 150 to XW m. 



of a large species (S. chlorostictus). Most (88-95%) of habi- 

 tat guild II occurred at shallow depth (75-175 ml; about 

 one-half of guild III occurred in water <175 m. Guilds IV 

 and V represented habitats of large structure, high 

 relief (78% occurrence), and both shallow and deep 

 (>175 m) water. Although they both had similar top- 

 ranked species, guild IV (boulder-mud) was much 

 less diverse and was dominated by a single species 

 (S. helvomaculatus). Economically valuable rockfish 

 species made up most (52-77% ) of guild V (rock hab- 

 itat). The rock habitat guild, in particular, contained 

 high numbers of large species up to 1 m in total 

 length, such as S. levis i 12% of total fish abundance 

 in this habitat) and S. ruberrimus (5% total abun- 

 dance). These fishes were closely associated with 

 ledges, caves, crevices, and overhangs. 



Fishes and habitat by site 



In general, our study area in Soquel Canyon com- 

 prised five sites of exposed rock ridge, boulder, cobble, 

 pebble, and mud bottom types (Fig. 5). From the 

 mosaic of side scan sonographs, total area of outcrops 

 ranged from 1.4 ha (site 5) to 19.6 ha (site 3), and 

 the sampling effort (i.e. number of dives, transects) 

 in these sites tended to vary accordingly. We quan- 

 titatively sui-veyed fish and habitat in 1025 sample 

 patches (average area of a habitat patch was 34.0 m-; 

 SE=1.9 m2), representing from 1285 to 13,626 m^ 

 per site. From analysis of 83 transects, 74-94% of 

 the bottom types at these sites were characterized 

 by mud, rock ridge, and combinations of both. Not 

 surprisingly, nearly 50% of our survey was in areas 

 of high relief, and almost all (97%) rock ridge was 

 high relief Mud habitats were largely (78%) of flat 

 and low relief 



Site 1, located on the east canyon wall at a water 

 depth from 98 to 305 m, was characterized as rock out- 

 crop with moderate vertical fracturing, stepped rock 

 ridges of 1-6 m height (habitat guild Vi, mud-cobble 

 and mud-boulder fields ( habitat guilds 11 and 111 ), and 

 mud terraces (habitat guild I). Directly opposite on 

 the west wall, site 2 included a series of rock ledges, 

 mud terraces, and vertical walls e.xtending from 263 

 to 148 m depth; this site is heavily fished (see later 

 criteria). Site 3 comprised small ledges interspersed 

 with mud, boulder, cobble, and pebble slopes of low 

 relief at 94—150 m, high-relief rock ledges with frac- 

 tures cutting the bedding planes and massive vertical 

 mudstone walls (150-250 m). and scattered boulder- 

 mud fields at the base of the wall. Sites 4 and 5 were 

 largely isolated outcrops of rock ridges surrounded by 

 fields of mud at 152-226 m depth. 



Rockfishes of various species ranked first in abun- 

 dance at all of the five study sites (Table 1); over all 

 habitat types and depth, at least three of the top five 

 species were rockfishes (4—5 of 5 at most sites). Aver- 

 age abundance was highest at site 5 (42.4 fish per 

 100 m-), 96'/; of which comprised economically valu- 

 able species (e.g. in rank order of abundance, S. pan- 



