Tinus Prey preference of Ophiodon elongatus, a top marine predator 
199 
Figure 3 
Proportional relative availability (dark bars) of potential prey as determined 
from nine dive surveys off Oregon for sites 1 and 2 combined, and propor- 
tional consumption (light bars) of prey by lingcod (Ophiodon elongatus) for 
sites 1 and 2 combined. The lack of overlap between realized consumption 
and relative availability indicates that lingcod were not preferentially 
consuming the most apparently abundant prey types, which were rock- 
fishes ( Sebastes spp.). 
consistently occurred in lingcod stomachs containing 
both octopus and shrimps, but never with flatfishes of 
any species. This pattern suggests that these lingcod 
did not forage for flatfishes directly over the seafloor, 
but were eating them in the water column. Because 
lingcod were captured on mid-water lures, they are 
apparently capable of foraging in the pelagic as well 
as the benthic zones. 
Prey preference 
Analysis of identified prey in the pooled data showed 
that prey selection was not proportional to availability 
(Johnson’s preference, F 13 132 = 943, P<<0.001). Rock- 
fishes were significantly “avoided” among prey categories 
(Waller-Duncan [1969] multiple comparisons, P =0.01, 
n = 145). In order of preference, adult rockfishes were 
ranked last followed by subadult rockfishes (Fig. 6). 
Preference ranking also indicated that transient and 
pelagic prey (Pacific herring and Pacific sandlance) were 
among the most preferred prey. The January surveys 
could not be temporally matched with consumption data 
and therefore were excluded from this analysis, as were 
empty stomachs. However, because of the inherent tem- 
poral and spatial patchiness of transient prey, as well as 
the difficulty in comparing very different types of prey, 
it was not possible to differentiate prey preference ranks 
among Pacific herring, Pacific sandlance, shrimps, and 
octopus. Other categories fell between these extremes 
(Fig. 6). 
Discussion 
These data indicate that lingcod off the coast of Oregon 
1) are highly generalized predators of both fish and 
invertebrates in multiple habitats; 2) select prey dis- 
proportionately to prey abundance; and 3) do not dif- 
ferentially target rockfish as prey. Rockfishes may not 
be preferred because, unlike any other identified prey 
items, they have robust, venomous spines (Smith and 
Wheeler, 2006). In this case, experimental manipulation 
of predator and prey densities at meaningful temporal 
and spatial scales is not possible. For this reason it 
is necessary to use consumption and relative density 
estimates in a static model to find evidence of an effect. 
If consumption is very low relative to prey abundance, 
as is the case with predation on rockfishes, then any 
