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Fishery Bulletin 1 10(2) 
direct effects on the population dynamics of either are 
unlikely to be strong. 
There is incomplete spatial and temporal overlap 
between prey availability and consumption data sets 
and the variance may be greater than it otherwise 
would be because the dive surveys are disjunct. Still, 
the MME beta value and asymptotic curve stability 
of the combined surveys suggest that the heterogene- 
ity of available prey can be detected with this level 
of effort and that the data are representative at this 
spatial and temporal scale. The prey availability data 
are not intended to reflect regional abundance. When 
a prey type such as Pacific herring is ranked low with 
respect to availability relative to rockfishes, it suggests 
rockfishes have more constant (less patchy) temporal 
and spatial overlap with lingcod. In this way the po- 
tential for encounter is much higher between lingcod 
and rockfishes. 
Large, highly generalized predators eat many differ- 
ent prey types and often do so infrequently, and there- 
fore sample sizes must be relatively large to adequately 
capture the heterogeneity of the consumption data (e.g., 
Kingsford, 1992). With 375 samples, the dietary data 
reported here describe the relative abundance of prey 
categories in the diet of lingcod over a limited geo- 
graphical area during half the year. However, Steiner 
(1979) collected summer and winter stomach samples 
and did not show an increase in lingcod consumption 
of rockfishes in winter and the number of samples col- 
lected appears to have captured the heterogeneity in 
the consumption data. The primary sources of error in 
these data include potential misidentification of prey 
and undefined rates of egesting stomach contents. Ad- 
ditionally, the digestion rates for free-living lingcod are 
unknown. Although they do reflect the relative temporal 
distributions of different prey types, the data from dive 
surveys were biased by both the spatial and temporal 
patchiness of transient prey, and by asymmetric sam- 
pling accuracy among habitats for prey types that were 
difficult to observe. However, rockfishes are highly ob- 
servable and there was clearly a strong negative prefer- 
ence (or avoidance) for rockfishes than for all other prey 
types. Hydro-acoustic tracking studies of black rockfish 
have shown they move less than a few hundred meters 
over periods of months (Parker et al., 2008). 
The gape-limitation hypothesis predicts that prey- 
size selection is consistent with optimal diet theory at 
the lower bound and the physical constraint of mouth 
size at the upper bound (Schmitt and Holbrook, 1984) 
and can be useful for predicting foraging behavior in 
fish (e.g., Persson et al., 1996). Larger lingcod tend to 
consume larger prey, but the gape-limitation hypothesis, 
or size-spectrum hypothesis (Scott and Murdoch, 1983), 
is not particularly useful for predicting prey selection 
in these animals because all sizes of lingcod eat small 
prey and lingcod consume parts of larger prey. Gape- 
limitation does not effectively predict which prey species 
or functional groups adult lingcod of different sizes will 
prefer to consume, nor do these data show a distinct 
shift to larger prey with increasing lingcod size. 
In relatively long-lived generalist predators such 
as lingcod, dietary sampling at temporal scales 
over two years may be required for meaningful 
patterns in consumption to emerge. The variance 
in consumption by local predators of transient 
prey is high and may be independent of regional 
prey abundance. If consumption of resident prey is 
relatively even over time, the resident prey types 
may provide a maintenance resource and more 
ephemeral prey may provide sporadic opportuni- 
ties for enhanced growth and reproduction. Addi- 
tionally, indirect effects can be important to the 
distribution of predators. Besides direct consump- 
tion, risk effects (modification of prey distribution 
or behavior because of a perceived predation risk) 
may have an important influence on community 
structure (Creel and Christianson, 2007; Madin 
et al., 2010). 
There is concern that lingcod predation may re- 
duce the efficacy of marine reserves in the recov- 
ery of some overfished populations of rockfishes. 
In a recent study that addressed this issue in 
Puget Sound, Washington, Beaudreau and Essing- 
ton (2007) found that in 560 lingcod (<30-108 cm 
TL) sampled inside and outside marine reserves, 
6.8% of the total number of prey items were rock- 
fishes. All individual rockfish identified to species 
were Puget Sound rockfish (S. emphaeus ) and 
0.4% of all prey were confirmed to be other spe- 
cies of Sebastes. The Puget Sound rockfish is a 
%F n 
Figure 4 
Percentage of lingcod ( Ophiodon elongatus) prey (%N) as a 
function of frequency of occurrence in the diet (%F 0 ). Prey 
categories are as follows: TP=transient-pelagic fishes (pre- 
dominantly Pacific herring [Clupea pallasii]); SF=skates ( Raja 
spp.) and flatfishes; S = sculpins (family Cottidae); R=rockfishes 
( Sebastes spp.); G=greenling (family HexagrammidaeXinclud- 
ing cannibalism by lingcod); 1= invertebrates; 0 = other (includ- 
ing uncategorized, unidentified fishes). TP, for example, was 
both a relatively large percentage of the overall diet, and also 
commonly occurred as a prey type among lingcod sampled. 
