Laurel and Blood: The effects of temperature on hatching and survival of larval Lepidopsetta polyxystra 
289 
HMB o.io mm 
Fan 0.20 
Egm 0.25 
i n o.3o 
I 1 0.35 
Figure 7 
The effects of temperature and hatch time (days into hatch cycle) 
on northern rock sole ( Lepidopsetta polyxystra) larvae yolk reserves 
at hatch (YA, mm 2 ). Values for YA are means 0±1 standard error) 
based on image analysis of larvae taken from three replicate 
tanks (10-15 larvae sampled per tank). 
but the incubation temperature, by way of mediating 
yolk reserves, may be an important factor in this re- 
lationship. Regardless, it appears that northern rock 
sole larvae have physiological adaptations to maximize 
the use of endogenous resources under cold conditions 
(i.e., <9°C). Similarly, the growth rates and swimming 
performance of juvenile northern rock sole remain rela- 
tively high at cold temperatures compared to other 
Alaskan flatfish species (Hurst and Abookire, 2006; 
Laurel et al., 2007). 
Conclusion 
Temperature and hatch rank had distinct effects on 
size-at-hatch and yolk reserves, but the effects on post- 
hatch survival were not fully explored. Temperature 
had multiple influences on northern rock sole larvae 
by affecting developmental rates, size-at-hatch, and 
metabolic demands on yolk reserves. In the absence of 
predators, optimal incubation temperatures for north- 
ern rock sole eggs and prefeeding larvae appear to be 
~2-5°C. However, the benefits of successful hatching, 
increased size-at-hatching, and reduced risks of star- 
vation need to be weighed against possible increased 
predation risk (e.g., stage dependent mortality; Houde, 
2008) and dispersal potential (O’Connor et al., 2007) 
at low temperatures. In addition, it will be interesting 
to compare these data with those of southern rock sole, 
especially since differing thermal responses may be an 
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0 
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CO 
S? 100 
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Days after hatching 
Figure 8 
Time to starvation of unfed northern 
rock sole ( Lepidopsetta polyxystra) 
larvae as a function of temperature 
(2°, 5°, 9°, and 12°C). Data points are 
means (±1 standard error) for three 
replicate tanks at each temperature. 
important regulator of adult latitudinal distributions 
and seasonal spawning patterns between these species. 
Collectively, these questions will be important areas of 
research in the light of changing environmental condi- 
tions in the North Pacific. 
