Tinus: Prey preference of Ophiodon elongatus, a top marine predator 
197 
sites. Aggregations of black rockfish ( S . melanops ) 
typically exceeded 100 individual adults and were 
the most common rockfish species. There was no 
evidence of a group effect between sites 1 and 2 
(one-way ANOSIM, global /? = — 0. 115; significance 
of sample stat. = 64.2%). An MME for species accu- 
mulation indicated sampling effort was sufficient 
to achieve a stable asymptotic curve (S max =17.94; 
/3= 0.72). In the pooled data, black rockfish were 
41.1% of a total of 2640 fish recorded in nine dive 
surveys. When Sebastes species were aggregated 
into a single prey category (demersal rockfishes) 
there was no difference in mean abundance 
between sites (two-sided (-test, P=0.84, df=7) or 
of lingcod abundance between sites (Mann-Whitney 
(7=26.5, P=1.0). There was a mean of 177.7 (stan- 
dard error [SE ] = 14 . 8 ) demersal rockfish and 4.3 
(SE = 0.33) lingcod observed at Site 1 and a mean 
of 148.8 (SE = 37.8) rockfish and 3.8 (SE = 0.98) 
lingcod at site 2. A rank concordance test of prey 
common to both sites was significant with respect 
to abundance of potential prey species between 
sites (Kendall’s rank concordance test, PcO.Ol, 
n = 16, s = 1.91). Striped surfperch (Embiotoca late- 
ralis) and yellowtail rockfish (S. flavidus ) were 
recorded only at site 1, whereas canary rockfish 
(S. pinniger) were observed only at site 2. Besides 
those species, the sites did not differ with respect 
to either the presence of potential prey species or relative 
abundance by genus, with the exception of significantly 
more sculpins (family Cottidae) at site 1 than site 2 
(Mann-Whitney (7=18.0, P=0.3). Geographic ranges of 
all species in this study are known to overlap both sites. 
The smallest lingcod sampled or observed on a reef 
was 42 cm TL. Lingcod may be retained by the fishery 
at 61 cm TL and larger. Although undersized lingcod 
were sampled by special permit at both sites, the com- 
mercially caught samples were biased toward larger 
lingcod and most of the lingcod sampled were within 
a relatively narrow size range, likely because the local 
lingcod population was rebuilding and was dominated 
demographically by only a few cohorts. Lingcod juve- 
niles settle onto a variety of habitats but were not ob- 
served on reefs. This is not surprising because lingcod 
are periodically cannibalistic, as shown in this and 
other studies. 
Dietary composition 
Of the 60 lingcod stomachs sampled at site 1, 12 were 
empty and 48 contained prey that were aggregated into 
10 categories. At site 2, of the 315 lingcod stomachs 
sampled, 177 were empty and 138 contained the same 
10 prey categories plus Pacific sandlance ( Ammodytes 
hexapterus) as a major prey item, as well as market 
squid ( Loligo opalescens ), Pacific lamprey (Lampetra 
tridentata), and northern anchovy (Engraulis mordax) 
as minor items (Table 2). Because both the number of 
samples and sampling effort was much greater at site 
2, it was expected that more prey types were found in 
c 50 
a Site 1 empty 
d Site 1 non-empty 
■ Site 2 empty 
■ Site 2 non-empty 
30 - 
t L t ■■ 
45 50 55 60 65 70 75 80 85 90 95 >95 
Lingcod total length (cm) 
Figure 2 
Lingcod (Ophiodon elongatus) total length (cm) and frequency 
of occurrence for empty and nonempty stomachs sampled at 
sites 1 and 2 off Oregon, 2003-05. Gear types were: multiple 
fishermen with single hooks and lines at site 1 (gray), and a 
commercial fisherman with multiple hooks and lines for site 
2 (black). Lingcod under the legal limit for total length (<61 
cm) were retained by permit at both locations, but were propor- 
tionately more abundant among sampled lingcod at site 1, and 
proportionately more lingcod stomachs were empty at site 2. 
lingcod from there (see Bock, 1987). There were pro- 
portionately fewer empty stomachs among captured 
lingcod, and lingcod were smaller on average at site 1 
than at site 2 (Fig. 2). Among prey categories common 
to both sites, there were significantly more Pacific her- 
ring (Clupea pallasii) consumed by lingcod sampled at 
site 1 than at site 2 (two-sided (-test, P=0.01, df=373). 
A rank concordance test was significant, indicating that 
prey consumption by category did not differ between 
sites (Kendall’s rank concordance test, P<0 .01, n = 15, 
s=2.03) and therefore the data were pooled for the pref- 
erence analysis. 
After sites were pooled, there were 21 identified spe- 
cies aggregated into 14 ecologically similar prey catego- 
ries. Among the 342 prey items found in 375 stomachs 
(50.4% of lingcod stomachs were empty) major prey 
items were Pacific herring, Pacific sandlance, unidenti- 
fied fishes, two-spotted octopus ( Octopus bimaculatus), 
and pandalid shrimps ( Pandalus spp.). All other prey 
groups, including rockfishes, each comprised less than 
five percent of the total gut contents (Fig. 3). A MME 
for species accumulation indicated that sampling effort 
was sufficient (S max =14.91; /3= 17. 2 1 ). Of the prey items 
that were measurable to total length, 14 were confirmed 
to be rockfishes. The largest of those was 28 cm (the on- 
ly potential adult), and none was estimated to be more 
than three years old based on published length-at-age 
curves (Love et al., 2002). Of the identified young-of- 
year rockfishes, five were of the “black-spot” group and 
one was a stripetail (S. saxicola). Nearly all rockfishes 
identified to species were S. melanops and less than 
two years old as inferred by length (Love et al., 2002). 
