Kneger Distribution and abundance of Sebastes spp. 



93 



fish/1000 m- of seafloor area at the four untrawlable sites, com- 

 pared with 4.5 rockfish/lOOOrrr at the three marginally- 

 trawlable sites and 2.8 rockfish/lOOOm 2 at the thirteen 

 trawlable sites (Table 3). Most small rockfish were over rugged 

 habitat: 88% (403) over cobble at trawlable sites, 71% (135) 

 over cobble and boulders at marginally-trawlable sites, and 

 86% (427) among ledges, coral, etc., at untrawlable sites (Table 

 4). Small-rockfish densities were minimal estimates because 

 rugged habitat blocked some fish from the observer's view. 

 Three other submersible studies noted use of rugged habitat 

 by small rockfish: Carlson & Straty (1981), Straty (1987), 

 and Pearcyetal. (1989). 



Trawl catches 



Seven trawlable sites and two marginally-trawlable sites were 

 sampled with bottom trawls. Trawl speed ranged from 5.5 to 

 6.5 km/h, and the trawl intersected at least three of the four 

 submersible transect paths at each of the nine sites (Fig. 3). 

 Total number of fish captured was 11,089; 65% (7162) were 

 rockfish (Table 5). Of the rockfish, 81% were Pacific ocean 

 perch: 5587 adults (>25cm) and 219 juveniles (<25cm). After 



trawl-caught rockfish were standardized to the 

 submersible rockfish categories, large rockfish, 

 small rockfish, and other rockfish comprised 

 90%, 9%, and 1% of the trawl-caught rockfish, 

 respectively. Other commonly occurring fish in 

 the trawl hauls were shortspine thornyhead 

 (17%), flatfish (13%), and walleye pollock (3%) 

 (Table 5). 



The composition of fish captured in trawls 

 and observed from the submersible were highly 

 correlated; correlation coefficients (r) for all 

 rockfish combined, shortspine thornyhead, 

 flatfish, and walleye pollock were 0.93, 0.86, 

 0.79, and 0.72, respectively (Fig. 4). These 

 high correlations indicate that bottom trawls 

 sampled the same fish species observed from 

 the submersible. 



Catch efficiency on rockfish 



Catch densities of large rockfish were highly 

 correlated with observed densities from the 

 submersible (r=0.88). Catch densities were 



Figure 3 



Submersible transect courses ( — ) and trawl paths 

 (-) at nine submersible sites where rockfish counts 

 made from a submersible were compared with 

 CPUE of bottom-trawl hauls, August 1989. Num- 

 bers refer to sites in Figure 1. 



