316 



Fishery Bulletin 92(2). 1994 



Results 



Physical habitat 



An area of approximately 10,521 m 2 was surveyed 

 from the submersible, of which 38% was wall, 47% 

 complex, and 15% sand-mud habitat. Area of cover- 

 age among habitat types differed with depth (Fig. 

 2). The area of complex and sand-mud habitat cov- 

 ered in the surveys decreased with depth whereas 

 that of wall habitat increased. Sand-mud habitat 

 was encountered only at depths of <60 m and the 

 median area surveyed among transects was zero. 

 Wall habitat was the only habitat type observed at 

 depths greater than 120 m. The slope of the sub- 

 strate was correlated with depth (Spearman rank 

 correlation: r s =0.37, P<0.001) and habitat (r s =-0.71, 

 P<0.001). This was evident in that wall habitat 

 found primarily in deep water provided vertical or 

 near- vertical relief (-70-90° slope), whereas complex 

 and sand-mud habitats in shallower depths provided 

 a graded substrate (-20-70° slope). 



The area of each type of habitat surveyed differed 

 among survey sites (Kruskal-Wallis: P=<0.001, 0.03, 

 and <0.001 for wall, complex, and sand-mud habi- 

 tat respectively). Elbow Point and McKenzie Bight 

 had similar habitats whereas Sheppard Point had 

 less wall and complex habitat and more sand-mud 



5 



DC 

 < 



200 - 

 180 - 



160 

 140 

 120 

 100- 



80 - 

 60 - 

 40 

 20 - 

 



NUMBER OF 

 TRANSECTS: 



□ COMPLEX 

 D WALL 



I 



I 



J 



I 



1 



?,. 



i 



// 



i 



21-40 41-60 61-80 81-100 101-120 121-140 

 DEPTH (m) 



5 2 



16 



16 



16 



13 



Figure 2 



Overall median area of survey coverage for com- 

 plex and wall habitat in relation to depth. Verti- 

 cal bars represent the interquartile ranges <Q 02 5 

 to Q 075 >- Median area of sand-mud habitat sur- 

 veyed was zero. 



habitat than the Elbow Point and McKenzie Bight 

 sites. 



At the time of the surveys, Saanich Inlet was not 

 anoxic although waters below 100 m were deficient 

 in dissolved oxygen (Liu, 1989) (Table 1). Hydrogen 

 sulfide was not present at any depths sampled in 

 the inlet. Temperature and salinity were relatively 

 stable below depths of 100 m. 



Depth, size, and density distributions 



Quillback rockfish represented 88% (681/770) of all 

 rockfish sighted and were observed at a median 

 depth of 54 m (Table 2). Density of quillback rock- 

 fish did not differ among depth intervals between 

 21-100 m (P=0.35) (Fig. 3A). Only three quillback 

 rockfish were seen at depths >100 m. In total, the 

 median size of 460 quillback rockfish was 23 cm 

 (Table 2). Quillback rockfish size was positively cor- 

 related with depth (^=0.23, P<0.001, rc=460) and the 

 density of small and large quillback rockfish varied 

 among depth intervals (P=0.01 and P=0.02 respec- 

 tively) (Fig. 3B). Density of small quillback rockfish 

 was similar to that of large quillback rockfish in the 

 21^40 m depth interval (P=0.66), but it was less at 

 depth intervals greater than 40 m (all P<0.05) (Fig. 

 3B). In contrast, the median density of large quill- 

 back rockfish at depth intervals between 41-100 m 

 was greater than their density in the 21-40 m depth 

 interval (Fig. 3B). 



Tiger rockfish, S. nigrocinctus, copper rockfish, 

 S. caurinus, yellowtail rockfish, S. flavidus, green- 

 striped rockfish, S. elongatus, and yelloweye rock- 

 fish, S. ruberrimus, all had median densities of zero 

 in 21-150 m depths in Saanich Inlet (Table 2). 



