Tinus Prey preference of Ophiodon elongatus, a top marine predator 
201 
very small species that matures in 1-2 years. It 
is a schooling species and is often found in high 
densities. It is not fished either recreationally or 
commercially and thus is not the focus of recovery 
efforts. The largest measurable rockfish in Beau- 
dreau and Essington’s (2007) study was 16.6 cm. 
Combined with the results from Steiner (1979) 
and this study, lingcod of any size rarely prey on 
larger-body roekfishes. Beaudreau and Essington 
(2007) state that model results suggest intensive 
lingcod fishing is likely to disproportionately al- 
leviate predation pressure on larger roekfishes. 
However, combined empirical evidence from this 
study and the two studies cited immediately above 
does not support this assertion. 
Of all prey items found in this study, only one 
was a potentially reproductive rockfish and it 
apparently had been ingested within 24 hours 
of capture. This ratio simplifies to less than one 
adult rockfish consumed per adult lingcod per 
year, whereas the dive surveys revealed an aver- 
age of 40 adult roekfishes living in the vicinity 
of each lingcod. If these ratios are representa- 
tive, they suggest that lingcod predation is not a 
primary source of mortality for nearshore adult 
roekfishes off the coast of Oregon. Nor do lingcod 
appear to be a primary source of mortality of 
juvenile or young-of-the-year roekfishes because 
they were only slightly more likely than adult 
roekfishes to be eaten by lingcod. Hobson et al. 
(2001) found predation by black rockfish, blue 
rockfish, and kelp greenling was the primary 
source of mortality for postsettlement juvenile 
roekfishes in northern California. 
50 
40 • 
40 50 60 70 80 90 100 
Lingcod length (cm) 
Figure 5 
Lingcod ( Ophiodon elongatus) total length (cm) versus prey 
length for each of 73 measurable prey items. The largest 
prey item was a Pacific giant octopus (Octopus dofleini) 
estimated at 70 cm in length that two individual lingcod, 
72 cm and 93 cm respectively, appeared to have each eaten 
half. This prey item is represented by two data points, each 
with an assigned prey length value of 35 cm. The slope 
of the regression line (adj. R 2 = 0.29) is influenced by the 
three largest prey items. Dashed lines represent the 95% 
confidence interval. 
Conclusions 
The results of this study show that lingcod are highly 
generalized predators that consume a broad variety of 
prey in terms of taxa, body form, and habitat. Lingcod 
are mobile, opportunistic, ambush predators that do 
not appear to be individually specialized. On the basis 
of the number of empty stomachs, they frequently go at 
least several days without eating, indicating there may 
be large differences between local prey abundance and 
prey availability (see Menge, 1972; Kelly, 1996). Better 
information is required on foraging range in relation 
to differences in habitat and prey availability to better 
understand lingcod foraging behavior as it relates to 
prey density. Nevertheless, this study strongly indicates 
that lingcod do not pose a threat to rockfish populations. 
EBFM requires more information than single-species 
management approaches. In data poor systems, and 
particularly those that are difficult to access, higher 
echelon data describing interactions among both tar- 
geted and nontargeted species will be very difficult to 
develop. However, this study shows that untested as- 
sumptions about trophic relationships may lead to coun- 
terproductive management decisions, particularly with 
respect to large predatory species (Baum and Worm, 
2009). Marine reserves can be an effective manage- 
ment tool for the conservation and recovery of exploited 
and other species, and particularly so where species of 
particular interest have relatively site-attached adult 
populations. In these cases trophic relationships, es- 
pecially among resident and transient species, are a 
critical uncertainty and these relationships can only be 
fully understood through both consumption and relative 
prey availability measures. In this case, a preference 
index provides much more information about the likely 
result of fluctuations in predator and prey populations 
than would be the case with diet data alone. 
Acknowledgments 
This study was funded in part by a Cooperative Institute 
for Marine Resource Studies (CIMRS) grant. I thank 
R. Cross, D. Edge, M. Hixon, and J. Miller for their 
helpful suggestions in the preparation of this manu- 
script; S. Reimers for help with sample identification; 
B. Gallagher, P. Heikkila, S. Heppell, K. Schultz, and 
S. Theberge for help with sample collection; E. Gilbert 
