Rooper et at: Estimating species and size composition of rockfishes to verify targets in acoustic surveys 
327 
OS 10 ■ 
Dusky rockfish 
(Sebastes variabilis), n - 22 
I 
0.20 0.40 0.60 
Harlequin rockfish 
( Sebastes variegatus), n-1 
>1.S 
tu 
1.0- 1.5 
7 
■HU 
1 1 1 
1.00 0.00 
Proportion 
Northern rockfish 
(Sebastes polyspinis), n - 21 
1.00 0.00 0.20 0.40 0.60 
Other rockfish, n = 18 
0.20 
1 Trawlable 
2 Untrawlable 
Figure 6 
Distribution of rockfish species by height off the seafloor (m) at the Snakehead Bank, Alaska, in 2009. These 
data were available only from the five stereo drop camera transects where both cameras were functional 
and where rockfish species were observed. The data for each depth and species are split into trawlable and 
untrawlable proportions based on the seafloor characteristics where the individual fish were observed. Other 
rockfish include Pacific ocean perch ( Sebastes alutus ), rosethorn rockfish (S. helvomaculatus), yelloweye 
rockfish (S. ruberrimus ), and dark rockfish (S. cihatus). n = no. of fish in sample. 
Table 3 
Chi-squared test for the random distribution of rockfish species between trawlable and untrawlable habitats. Data from stereo 
drop camera (SDC) and remotely operated vehicle (ROV) deployments (n = 12). Shown are the observed frequency and expected 
frequency of rockfish for each species that occurred in trawlable areas, based on the amount of trawlable area surveyed with the 
SDC and ROV are shown. 
Species 
Observed frequency 
in trawlable areas 
Expected frequency 
in trawlable areas 
Dusky rockfish ( Sebastes variabilis ) 
157 
479 
Northern rockfish (Sebastes polyspinis ) 
130 
71 
Harlequin rockfish (Sebastes variegatus) 
0 
127 
Pacific ocean perch ( Sebastes alutus ) 
1 
46 
Other rockfish: yelloweye (Sebastes ruberrimus ), 
redstripe (S. proriger ) redbanded (S. babcocki ), 
dark (S. ciliatus), tiger (S. nigrocinctus), 
and rosethorn rockfishes (S. helvomaculatus) 
1 
59 
Number of fish observed /j 2 
1960 
366 
X 2 (critical value, P= 0.05, df= 1 1 ) 
19.68 
because these species are unavailable to both acoustic 
and bottom trawl surveys. 
Temporal and spatial variability in species distribu- 
tion may have influenced the results of comparisons 
of species distribution by gear types in this study. Al- 
though each of the gear types was deployed at a slightly 
different combination of sites over the same relatively 
small area of the Snakehead Bank, each gear type was 
