Yoklavich et al : Habitat associations of deep-water rockfishes 



631 



42). 

 10)1 



17)1 



Dominant 

 Species 



% 



S. saxicola (42) 

 Microslomus paaticus ( 

 Agonidae ( 

 Sebaslolobus alascanus ( 7) 



S semicinclus (19)^ 

 S. e/ongams (18) I 



S. w/soni (11) J 



S. saxicola (20) 



S helvomaculatus (15) 



Agonidae (1 1 ) 



S. chlorosticlus ( 7) 



S. elongalus ( 7) 



S. helvomaculatus (40) 



S. chlorosticlus (11) 



S. paucispinis (10) 



)'" { 



} 



S paucispinis (22) 



S helvomaculatus (14) 



S cWorosf/cfus (13) 



IV 



>■( 



S. w/teora (42) ■» 

 S. paucispinis (1 8) J VI 



Habitat 

 Guilds 



Mud 



Cobble-Mud 

 I Mud 



Pebble 



Mud-Cobble 



Mud-Rock 



Boulder-Mud 



Mud-Boulder 



Rock-Mud 



Rock ridge 



Rock-Boulder 



Dissimilarity 



Figure 4 



Cluster dendogram that groups standardized abundance (number per 100 m^) of nonschooling benthic fish species in Sequel 

 Canyon, based on associated type of bottom substrata. Dominant species (percent relative abundance in parentheses) of the 

 six main habitat guilds are indicated. See Figure 8 for number of habitat patches sampled in each habitat. 



cispinis, O. elongatus, S. levis. S. rosenblatti. S. chlorostictus, 

 S. ruberrimus). These sedentary fishes were primarily shel- 

 tered under ledges, in crevices, and among large sea anemo- 

 nes (Metridium giganteum ) on this isolated rock outcrop. 



One objective of our study was to compare species com- 

 position, abundance, size, and diversity of fishes among 

 sites receiving var)dng amounts of fishing pressure within 

 the canyon. Seventy-five lines (polypropylene and monofil- 

 ament; n=&l) and cables (?!=8) were observed on 83 tran- 

 sects during 13.5 h; no mesh nets, pots, or trawl tracks were 

 found. Eighty-five percent of these sightings occurred at site 

 2, with 26.7 observations of gear made per hour of survey 

 (or 0.9 sightings per 100 m^). Observations of 1.5 and 0.7 

 per hour were made at sites 3 and 1, respectively. No evi- 

 dence of fishing gear or activity was found at sites 4 and 5. 

 These observations are supported by California Department 

 of Fish and Game (CDFG) records of site-specific activities 

 of commercial passenger fishing vessels (Reilly-). 



From the cluster analysis, economically important rock- 

 fishes are largely represented by the rock habitat guild 

 (V). After limiting statistical comparisons among sites to 

 those species occurring on mud-boulder, rock-mud, and 

 rock ridge bottom types (i.e. habitat guild V), we found 

 abundance of each of the top eight species in this guild 

 (Fig. 6) varied significantly among sites (AN OVA or ran- 

 domization test; P<0.01 ). Large solitary and sedentary spe- 

 cies, such as S. chlorostictus, S. riibei-rinuis, and S. levis. 



~ Reilly, P. 1997. Personal common. CDFG, 20 Lower Rags- 

 dale Dr., Monterey, CA 93940. 



were most abundant at sites 1, 3, 4, and 5, which received 

 minimal to no fishing pressure. Abundances of these three 

 species were statistically less at site 2, the area of highest 

 fishing activity. 



Sebastes paucispinis, one of the most important species 

 in commercial and recreational fisheries of Monterey Bay, 

 occurred in high numbers at all sites but was significantly 

 more abundant at site 5 ( Fig. 6; randomization test, P<0.0 1 ). 

 Although we limited our study to nonschooling individu- 

 als, S. paucispinis can be semipelagic and we sometimes 

 encountered this species in loose groups of 50 or more fishes 

 above rock outcrops. These groups were not included in our 

 analysis but indicate that this species is more active and 

 broad ranging than the solitary benthic rockfishes. 



Interestingly, the most abundant species at the site most 

 heavily fished (site 2) was S. helvomaculatus, a relatively 

 small species and historically of minor interest to either 

 commercial or recreational fisheries. This species also was 

 significantly more abundant at this site than at any of the 

 other four sites (Fig. 6; resampling test, P<0.01). Sebastes 

 crameri and S. riifus, relatively important rockfish species in 

 the commercial trawl fishery but rarely taken by hook and 

 line, were abundant only at site 2 (ranking second and fifth, 

 respectively). Sebastes elongatus. a relatively small species 

 that was most abundant in the cobble-mud guild, was mod- 

 erately abundant in the rock guild but only at sites 1-3. 



Size of most of these species differed by site and depth 

 category (shallow=75-174 m; deep=175-275 m; Fig. 7). 

 Significantly smaller individuals of S. chlorostictus, S. hel- 

 vomaculatus, S. elongatus, and S. paucispinis occurred 



