Lee and Sampson: Dietary variations for three rockfish species off the Pacific Northwest 
511 
Table 1 
The number of rockfish stomach samples collected from commercial fishing trawlers off the Oregon coast by seasonal quarter and 
from the NMFS 1998 summer survey cruises off the Oregon and Washington coasts. The numbers of nonempty stomach samples 
are provided in parentheses. 
Sampling dates 
Fishing vessel 
No. of stations 
Sebastes flavidus 
Sebastes entomelas 
Sebastes pinniger 
5-8 Apr 1998 
Pacific 
12 
31 (29) 
60(37) 
17(15) 
6-9 Aug 1998 
Kelly Girl 
6 
31 (29) 
56(48) 
29 (24) 
8-9 Nov 1998 
Pacific 
7 
24(16) 
37 (24) 
13 (11) 
13-14 Feb 1999 
Pacific 
6 
9(7) 
26 (7) 
10(9) 
6-7 Apr 1999 
16-18 Apr 1999 
Pacific 
11 
54(45) 
48 (46) 
27 (6) 
13-16 Sep 1999 
Pacific 
7 
18 (13) 
47 (32) 
8(0) 
Subtotal of quarterly 
49 
167(139) 
274 (194) 
104(65) 
fishery sampling 
27 Jun-7 Aug 1998 
Dominator Vesterallen 
56 
360(312) 
— 
— 
(NMFS survey) 
(Mackas and Galbraith, 2002; Keister and Peterson, 
2003; Keister et al., 2005). With major changes in en- 
vironmental conditions, and consequent changes in 
zooplankton abundance and community structure, one 
would expect to observe changes in the food habits of 
planktivorous fish species. 
The objectives of this study were 1) to describe the 
food habits of three commercially important rockfish 
species (yellowtail [S. flavidus], widow [S. entomelas ], 
and canary [S. pinniger ] rockfish) over the study period 
(1998-99), during which the ocean environment under- 
went considerable changes, 2) to examine the relation- 
ship in these rockfish species between dietary variation 
and extrinsic factors: spatial (depth, latitude), temporal 
(time of day, season, year), and biological (predator type, 
sex, fish size), and 3) to compare the diets of S. flavi- 
dus collected during El Nino year 1998 with the diets 
reported during 1980, a non-El Nino year (Brodeur and 
Pearcy, 1984), to examine possible changes between the 
two periods. 
Materials and methods 
Data collection 
There were two different types of sampling sources 
for the study: quarterly fishery samplings and U.S. 
National Marine Fisheries Service (NMFS) summer 
surveys. These data sets were maintained and analyzed 
separately. From the quarterly fishery samplings, 
stomach samples of three rockfish species, S. flavidus, 
S. entomelas, and S. pinniger, were collected off the 
Oregon coast during seven fishing trips aboard Oregon 
trawlers over six consecutive quarters from spring of 
1998 to fall of 1999. Each trip consisted of two to four 
days of fishing. A total of 398 nonempty stomach samples 
of the three rockfish species were collected from 49 dif- 
ferent stations over the six quarters. From the 1998 
NMFS summer bottom trawl survey, stomach samples of 
only one rockfish species (S. flavidus) were collected off 
the Oregon and Washington coasts, and 312 nonempty 
stomach samples were collected from 56 stations during 
this survey (Table 1). Additional data on S. flavidus were 
obtained from stomach contents samples collected off 
Oregon and Washington during the 1980 summer NMFS 
survey (R. Brodeur, personal commun. 1 ). The data were 
made available at the individual stomach level (128 
nonempty stomach samples) and were compared with the 
1998 summer NMFS survey data on S. flavidus. 
The NMFS samples were collected at stations allo- 
cated by a systematic random design. The survey area 
was divided into three depth strata: continental shelf 
(55-183 m); shelf break (184-366 m); and uppermost 
continental slope (366-500 m). Stations were randomly 
assigned along tracklines laid across the depth strata, 
with at least one station assigned to each depth stra- 
tum along each trackline segment. Each trawl haul was 
made for 30 minutes at a given station. In contrast, for 
the quarterly sampling aboard the commercial fishing 
boats, the fishermen selected the trawling stations on 
the basis of sonar detection of large schools of rock- 
fishes on the bottom. These different sampling schemes 
resulted in different coverage of the study area. The 
quarterly fishery samplings covered a confined area off 
the Oregon coast, whereas the NMFS survey covered a 
wider range of coastal waters (Fig. 1), but only during 
summer. 
Individuals of the three targeted rockfish species 
were randomly selected from the catch and their stom- 
achs were removed at sea. Before a stomach was re- 
moved, the buccal cavities were examined for evidence 
1 R. Brodeur. 2001. National Marine Fisheries Service, 
Northwest Fisheries Science Center, 2030 S. Marine Science 
Dr., Newport, OR 97365-5296. 
