196 
Fishery Bulletin 1 10(2) 
2 were by a commercial fisherman in the months of May 
(21 fish), June (48 fish), and October (59 fish) of 2004, 
and May (49 fish), June (45 fish), August (46 fish), and 
October (40 fish) of 2005 (Table 1). The commercial gear 
used was a “dingle-bar” — an iron bar trolled just off the 
seafloor with a set of three rubber jigs with large hooks 
and an attractor. An additional set of three jigs with 
hooks was trolled mid-water (about 10-20 m off-bottom). 
When multiple lingcod hit the jigs, they generally did so 
simultaneously on both the bottom and mid-water sets. 
In the first year, lingcod stomachs were labeled, 
placed in cloth bags, and preserved in ethanol. In 
subsequent years, stomachs were labeled, wrapped 
in cheesecloth, packed in ice, and examined within 
24 hours. The number and identity of items in each 
stomach were identified to the lowest possible taxon. 
When the identification of a prey fish was not possible 
from external characteristics, I attempted to identify 
the prey by otoliths or skeletal elements (or both). A 
second, blind reading of a subsample of otoliths and 
skeletal elements was done by a recognized expert who 
confirmed prior determinations. When possible, beaks 
were used to estimate size and infer species of octopus 
by comparison with other samples that were identified 
to species from external characteristics. 
Observed consumption provides a description of a 
local prey base if sample sizes are large enough to cap- 
Table 1 
Dates and locations of dive surveys and stomach collec- 
tions for diet samples of lingcod (Ophiodon elongatus ) in 
the nearshore zone off the Oregon Coast. Site 1 is located 
south of Newport, OR, and site 2, south of Coos Bay, OR. 
An X indicates that data were collected. Data used for 
prey preference analysis are within-season. 
Dive survey Diet samples 
Site 
Date 
X 
1 
16/07/03 
X 
1 
23/07/03 
X 
1 
25/08/03 
X 
1 
24/09/03 
X 
1 
09/01/04 
X 
2 
22/01/04 
X 
2 
24/05/04 
X 
1 
09/06/04 
X 
2 
24/06/04 
X 
2 
05/10/04 
X 
2 
22/10/04 
X 
2 
13/05/05 
X 
2 
03/06/05 
X 
2 
08/06/05 
X 
1 
22/06/05 
X 
2 
26/06/05 
X 
2 
27/06/05 
X 
2 
17/08/05 
X 
2 
28/09/05 
X 
2 
20/10/05 
ture the diversity within a population and incorporate 
representative temporal and spatial scales. Although 
lingcod are highly generalized, the incidence of new 
prey types in gut samples was asymptotic with in- 
creasing sample size. The MME was used to generate 
a species-accumulation curve and test for sufficiency of 
sampling effort. A rank concordance test of prey cat- 
egory abundance was conducted for sites 1 and 2 (Sokal 
and Rohlf, 1995). For comparisons of two groups, /-tests 
were used unless a Shapiro-Wilk test for normality or 
equal variance test (or both) failed, in which case a 
Mann-Whitney rank sum test was used. Additionally, 
one-way analysis of variance (ANOVA) was used to test 
for differences among sampling trips for differences in 
stomach fullness and for differences in consumption of 
transient and resident prey types. 
Stomach content data were analyzed by frequency of 
occurrence, %F o - (n-100)/N s ; and percentage of prey, 
%N = (n'-100)/Af p ; where n=the number of stomachs 
containing a particular prey type, N s =the total number 
of lingcod stomachs examined, n'=the total number of 
individuals of a particular prey type, and W p =the total 
number of prey items (Hyslop, 1980). 
Prey-preference model 
A preference model describes the relative selection 
of resources in relation to the availability of those 
resources. If a particular prey type is selected more or 
less frequently than would be predicted by relative avail- 
ability, that prey type is said to be either preferred or 
avoided relative to other prey types. The general formu- 
lation of the preference model (Johnson, 1980) is as fol- 
lows. Let r - be the rank of some measure of consumption 
of prey component (i) by an individual predator (J) and 
s (/ be the rank of an observed measure of the availability 
of prey component (i) to individual predator (j). The indi- 
vidual differences in these ranks, t tJ = r tJ - s y , are then 
averaged across animals to indicate the relative prefer- 
ence of all prey types across all predators, as given in 
Equation 1 below. The advantage of this nonparametric 
approach is that information about prey preference can 
be gleaned from imperfect field data. The use data and 
availability data are ranked for each animal and even 
if a particular prey type is not observed, those data can 
be used in the analysis. If a known prey type was not 
observed, the availability of that particular prey type 
would be considered low by comparison with other prey 
types in the analysis. 
I = Z (r v - s y )/J - (1) 
Results 
Prey availability 
Observed fish abundance was overwhelmingly dominated 
(over 90%) by demersal rockfishes ( Sehastes spp.) at both 
