386 
Fishery Bulletin 108(4) 
Temperature (°C) 
Figure t 
Temperature-dependent growth rates of preflexion 
larval Pacific cod ( Gadus macrocephalus ) in (A) stan- 
dard length and (B) dry mass. Fish used in experiments 
were the offspring of spawning adults collected in the 
central Gulf of Alaska in April 2007 (open symbols) 
and 2008 (filled symbols). Values are the mean growth 
rates (±standard error) for three replicate tanks at four 
temperatures. Overlapping points are displaced hori- 
zontally for clarity. 
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Figure 2 
Temperature-dependent growth rates of postflexion 
larval Pacific cod ( Gadus macrocephalus) in (A) standard 
length and (B) dry mass. Fish used in the experiment 
were the offspring of spawning adults collected in the 
central Gulf of Alaska in April 2007. Values are the 
mean growth rates (+standard error) for three replicate 
tanks at four temperatures. Symbols represent groups 
based on initial size sorting of larvae (circle: small; 
triangle: medium; square: large). Overlapping points 
are displaced horizontally for clarity. 
P<0.001). Differential growth during the temperature 
acclimation period resulted in slight differences in initial 
sizes among temperature treatments (treatment mean L T 
range: 48.8-51.8 mm; F| 3 83 ]=2.70, P=0.051). Although 
there were significant differences in growth rates among 
tanks within temperature treatments, these were not 
consistent across size groups, resulting in a significant 
interaction between temperature and size group (g M 
[ 6 , 60 ] = 2 . 2 3 , P= 0.052; g L : Pj 6 60 j=2.34, P=0.042). 
Growth in length and mass of juvenile Pacific cod was 
significantly affected by rearing temperatures across 
the range examined (Fig. 3; g M F [36] = 59.3, P<0.001; 
g L (F[ 36 ] = 26.7, PcO.001). Growth rates at 11°C aver- 
aged 2.9 and 3.7 times (g M and g L , respectively) greater 
than those observed at 2°C in similar size treatments. 
Best-fit functions describing growth as a second-order 
function of temperature are shown in Table 2. 
General growth model 
Models of growth rates of early life stages of Pacific cod 
indicated a discontinuity from strict allometric scaling 
during the early larval stage. Growth rates of preflex- 
ion larvae were lower than predicted based on a purely 
ontogenetic model incorporating growth-rate data from 
embryos to settled juveniles. Therefore, two-stage models 
were developed to describe growth in the egg stage 
separately from the posthatch, free-swimming stages. 
Although growth was a function of both temperature 
and body size, it was effectively modeled as the product 
of independent functions of temperature and body size. 
There were no significant interactions in the sense that 
the parameters of the temperature-dependence function 
were not themselves a function of body size. Therefore, 
embryonic and free-swimming stages shared a single 
