Laurel and Blood: The effects of temperature on hatching and survival of larval Lepidopsetta polyxystra 
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pigment patch on the dorsal half of the body is at 50% 
SL and a band is present at 75% SL. Below the patch 
and band are corresponding patches of pigment just 
above the ventral edge of the anal fin; anterior anal- 
fin pigment spots are more closely spaced than those 
within the posterior patch. A single row of PVMs is 
present starting at three myomeres posterior to the 
anus. These PVMs are spaced at approximately one 
per myomere and stop just beyond the pigment band 
at 75% SL. There are 4 or 5 PVMs along the last 3 
or 4 myomeres. Pigment may be present on the noto- 
chord and is variable; there may be 1 or 2 spots on 
the ventral margin, 1 spot on the dorsal margin near 
the tip of the notochord, pigment only on the upper or 
lower margin, or no pigment may be present. Overall, 
northern rock sole larvae have less pigment on the 
postanal portion of the body than southern rock sole 
and can easily be differentiated. Southern rock sole 
larvae have an additional dorsal pigment patch 1-5 
myomeres after the anus and a dorsal patch or caudal 
bar at the posteriormost myomere. Subsequent descrip- 
tions of preflexion, flexion, and postflexion stages of 
both rock sole species are found in Orr and Matarese 
( 2000 ). 
Hatching patterns 
Successful hatching was observed in all of the tem- 
perature treatments, but hatch patterns (time to first 
hatch, peak hatch, and hatch duration) were nega- 
tively related to temperature as indicated in the series 
of exponential decay, two-parameter models shown 
in Figure 3 (see Table 1 for model parameter esti- 
mates). Hatch quality and hatching success were also 
negatively associated with temperature (Fig. 4; Table 
1), largely driven by the high numbers of malformed 
larvae (>50%) observed in the 12°C treatment. Mal- 
formed larvae were alive but curved in appearance and 
had poor swimming capabilities shortly after hatching. 
A subset of malformed larvae held over the course of 
the hatch cycle continued to swim poorly and did not 
appear to straighten out during the entire yolksac 
period. Despite the malformation, these larvae sur- 
vived approximately the same length of time in the 
absence of food as normally formed larvae held at the 
same temperature (~7 days; see below). 
Size-at-hatch and yolk reserves (yolk area; [YA]) 
were a function of both temperature and timing in 
the hatch cycle. Overall, larval size-at-hatch ranged 
from 2.95 to 5.43 mm SL among all temperature treat- 
ments, but larvae were larger if they were late hatch- 
ing or were incubated in colder water (Fig. 5). The 
maximum size-at-hatch achieved over the course of 
the hatch cycle occurred at 5°C (Fig. 6) and was best 
described by a Gaussian model (Table 1). However, the 
temperature effect was more apparent in late-hatching 
larvae as indicated by the significant interaction term 
(Table 2). 
Yolk area also significantly varied as a function 
of temperature and hatch timing (Fig. 7), although 
the patterns were more variable than hatch size and 
there was no significant interaction between the two 
model terms (Table 2). Yolk reserves were larger in 
the early part of the hatch cycle and at warm incuba- 
tion temperatures. However, although not statistically 
described in the model, larvae hatching on the sec- 
ond day of the hatch cycle in the 12°C treatment had 
larger yolk reserves than those hatching on day 1. In 
all other temperature treatments, larvae hatching on 
successive days had reduced yolk reserves. 
Eye diameter varied between 0.22 and 0.33 mm and 
did not vary as a function of temperature or hatch 
rank (Table 2). However, larvae tended to have larg- 
er eyes later in the hatch cycle across all tempera- 
tures, although this was not statistically significant 
(P= 0.066). Larger and late-hatching larvae also ap- 
peared to have more eye pigmentation than small, 
early-hatching larvae. 
The posthatch survival time of larvae was negatively 
temperature dependent (Fig. 8), ranging from 12 to 
34 days among temperature treatments. Survival pat- 
terns followed a type-III functional response for each 
temperature treatment, and there was little variability 
among replicates. Plots of M 50 (point of 50% mortality) 
with temperature were described with an exponential 
decay model with an R 2 =0.99 (Table 1). 
