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Fishery Bulletin 109(3) 
sufficient larvae were available for the containers and 
morphometric measurements. Daily mortality was mea- 
sured by counting and removing dead larvae from each 
container bottom with a pipette. 
Data analysis 
The general linear model (GLM) was used to determine 
statistical differences in size (SL, mm), yolk area (YA, 
mm 2 ) and body depth (BD, mm) as a function of tempera- 
ture and hatch rank. Hatch rank (HR) was calculated 
for each temperature treatment by dividing the hatching 
day by the total number of hatching days observed at 
that temperature. All analyses were performed on tank 
averages and residuals were checked to ensure the data 
met the assumptions of normality of the GLM. Data 
were plotted in three dimensions to capture the nature 
of significant trends and interactions. 
Hatch characteristics (days to first hatch, hatch cycle 
duration, days to peak hatch, hatch quality, and hatch 
success), posthatch survival (i.e., time 50% mortality 
[M 50 ]) and maximum size achieved by yolksac larvae 
(S max ) were all analyzed by using linear and nonlin- 
ear regression tools in SigmaPlot, vers. 10.1(Systat 
Software, Inc., San Jose, CA). Model types (e.g., expo- 
nential, Gaussian, etc.) were initially selected on the 
basis of equivalent temperature relationships between 
eggs and larvae of other cold-water marine fish species 
(Jordaan and Kling, 2003; Laurel et al., 2008). The 
number of parameters in the statistical models were 
then chosen by using the Akaike information criterion 
(AIC; Akaike, 1974). The AIC value provides a rela- 
tive goodness-of-fit to a range of models but penalizes 
models that use additional parameters to explain small 
amounts of variance. Models were ultimately selected 
if the correlation coefficient (i? 2 ) values were greater 
than 90% and their AIC values were within 2 of the 
minimum in the range of compared models. All model 
fits were performed on raw data. 
Results 
Taxonomic description of eggs and newly hatched larvae 
Egg development from fertilization to middle-late stage 
(tail IV4-IV2 of the way around the yolk) has been 
described by Pertseva-Ostroumova (1961). Late-stage 
eggs from our study are 0.96-1.10 mm in diameter and 
overlap with reported egg sizes for the genus Lepidop- 
setta (0.86-1.08 mm; Orr and Matarese 2000). Just 
before hatching, the tail of the embryo is 1 3 A of the 
way around the yolk and the tail tip is even with the 
posterior margin of the eye. Pigment on the head is 
restricted to the snout, extending from just below the 
nares to the midbrain (Fig. 1A). The eyes are partially 
pigmented; a patch of larger melanophores is present 
on the anterodorsal quadrant and smaller fine melano- 
phores are scattered over the dorsal half of the eye and 
concentrated along the upper rim of the lens (Fig. IB). 
Figure 1 
Illustrations of (A) front 
view, and (B ) side view of a 
late-stage northern rock sole 
(. Lepidopsetta polyxystra ) egg 
measuring 1.02 mm diameter 
(32 days after fertilization at 
2°C). Illustrations by A. Maust, 
National Marine Fisheries Ser- 
vice, Alaska Fisheries Science 
Center. 
Dendritic pigment is present along the posterior 
dorsal gut margin, vent margin, and on the ventral 
yolk sac. A dorsal patch of pigment is located at 50% 
body length (BL) and a band of pigment is present 
at 75% BL; below both the patch and band is corre- 
sponding pigment on the anal fin. A row of postanal 
ventral melanophores (PVMs) extends from the anus 
to the band at 75% BL. A small group of spots is pres- 
ent on the ventral body margin near the last 2 or 3 
myomeres and an additional 3 or 4 spots are located 
along the ventral margin of the notochord beyond the 
last myomere. The most posterior spot is near the end 
of the notochord. 
Newly hatched larvae (Fig. 2) have light dendritic 
pigment on the snout from the midbrain to the edge of 
the lower jaw. Pigment outlines the lower jaw, which is 
not yet open. Eyes are moderately pigmented; pigment 
around the lens, in the dorsoanterior quadrant, and 
at the posterior edge of the eye is darker. The lower 
lateral and ventral yolk sac is lightly pigmented with 
dendritic melanophores. The same type of pigment is 
present on the posterior edge of the yolk sac and on 
the dorsal area of the hindgut close to the body. A 
