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nibalism. Also, the amount of cannibalism generally 
increased with increasing temperatures; however, the 
amount of cannibalism on age-1 pollock was low dur- 
ing the warm years of 2000-2005, possibly because of 
the reduced abundance of both large and small pollock. 
The revised oscillating control hypothesis (Hunt et ah, 
2002, 2011) and studies of age-0 pollock diet (Moss et 
al., 2009; Coyle et ah, 2011) predict that during warm 
years there is increased top-down control of age-0 pol- 
lock (<150 mm) in the upper water column, but these 
studies do not address cannibalism of demersal, age-1 
pollock. 
In the fall, cannibalism on age-0 pollock is high and 
influences year-class strength (Dwyer et ah, 1987) and 
age-1 pollock cannibalism occurs, but is less prevalent 
(Dwyer et ah, 1987; Bailey, 1989). During summer 
months, age-1 pollock comprise the majority of can- 
nibalized prey pollock (Dwyer et ah, 1987). Mueter et 
ah (2006) found that predation (including cannibalism) 
of age-1 pollock by multiple predator species explained 
up to 76% of the variability in survival estimates (log- 
transformed recruit per spawner biomass) and conclud- 
ed that cannibalism was a significant factor affecting 
the survival of pollock. To explore the possibility that 
cannibalism on age-1 pollock in summer months affects 
year-class strength, we examined the relationship be- 
tween summer cannibalism and the abundance of age-1 
recruits from the stock assessment model (lanelli et ah, 
2011). In our study, there were significant, positive re- 
lationships between the number of age-1 recruits and 1) 
the amount of pollock cannibalized (r 2 =0.40, 0.49, and 
0.39; and P= 0.001, <0.001, and 0.001, for %BW lgPollock , 
%FO L g Poiiock > and PF L g Poiiock > respectively) and 2) the 
proportion of stations where cannibalism was present 
(r 2 =0.53, P<0.0G1; Fig. 8). The occurrence and amount 
of cannibalism increased significantly with increasing 
age-1 recruit abundances, suggesting that cannibalism 
on age-1 pollock is not controlling recruitment, and 
strong year classes may overwhelm the capacity for 
cannibalism. These results imply that summer canni- 
balism of age-1 pollock, a top-down process, is not the 
sole determinant of age-1 pollock abundance. 
In this study, we found that the occurrence and 
amount of cannibalism observed in the survey diet 
samples were good indicators of year-class strength, 
because when there were more age-1 pollock consumed, 
the predicted abundance of age-1 recruits in the stock 
assessment model was higher. The relationship between 
the small pollock CPUE ( SmallPollock ) in the bottom 
trawl survey and the abundance of age-1 recruits from 
the stock assessment model is also significant and posi- 
tive (r 2 - 0.26, P=0.013; Fig. 8); however, SmallPollock 
does not explain as much variability in age-1 recruit 
abundance from the stock assessment model as the 
occurrence of cannibalism does. This result is likely 
due to the selectivity of the survey bottom trawl net, 
from which smaller fish may escape. Adult pollock are 
thus better samplers of age-1 pollock because the oc- 
currence and amount of cannibalism is indicative of 
age-1 abundance. 
Acknowledgments 
We would like to thank G. Lang, NMFS, for providing 
diet data, A. Greig for providing water column variables, 
G. Walters, NMFS, for providing initial data on water 
column temperature profiles, and P. Sullivan (Joint 
Institute for the Study of the Atmosphere and Oceans 
[ JISAO] ), P. Stabeno (PMEL), and M. Spillane (JISAO) 
for helping with temperature profiles. We also thank K. 
S. Chan at the University of Iowa for allowing us to use 
the “tgam” package he developed for R. This manuscript 
was significantly improved through the incorporation 
of comments from three anonymous reviewers. We also 
thank our funding sources: NOAA’s Fisheries and the 
