A manned submersible was used in the eastern Gulf of Alaska to observe
spatial distributions of Pacific ocean perch Sebastes alutus and othe
r Sebastes spp., and count rockfish for comparison with bottom-trawl c
atch rates. Twenty submersible dives were completed in 1988 and 1989 a
t depths of 188-290 m. Approximately 80% of the 5317 rockfish observed
from the submersible were Pacific ocean perch. Most adult Pacific oce
an perch were in groups of 2-200 over flat, pebble substrate. Fish wit
hin a group were 1-4 m apart, usually oriented into the current, and 0
-7 m above bottom. Most juvenile Pacific ocean perch, and juveniles an
d adults of other Sebastes spp., were associated with rugged habitat (
cobble, boulders, pinnacles, and coral). Densities of Pacific ocean pe
rch estimated from bottom-trawl catches were approximately twice those
observed from the submersible, indicating that the bridles and otter
doors herded fish into the trawl. Bottom-trawl surveys may overestimat
e Pacific ocean perch abundance because of this possible herding effec
t and the preference of adult Pacific ocean perch for smooth (trawlabl
e) substrate.