Laurel and Blood: The effects of temperature on hatching and survival of larval Lepidopsetta polyxystra 
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data for northern rock sole are available for stocks in 
the western Bering Sea (Pertseva-Ostroumova, 1961), 
but these data, in addition to not being geographically 
representative of Alaskan waters, are incomplete to 
develop a full temperature-development model. Descrip- 
tions of late-stage eggs and newly hatched larvae are 
also absent for northern rock sole larvae in Alaskan 
waters despite their commercial importance. Therefore, 
the objectives of this study were 1) to provide a descrip- 
tion of late-stage eggs and newly hatched northern rock 
sole larvae from laboratory reared specimens, and 2) 
to measure and model temperature effects on develop- 
ment rate, survival, and morphometric features (e.g., 
hatch length, condition, yolk volume) of eggs and newly 
hatched northern rock sole larvae from the eastern 
Pacific Ocean (Gulf of Alaska). 
Materials and methods 
Broodstock collections 
Adult northern rock sole (n= 25; 32-40 cm total length 
[TL]) were collected at 30-m depth by trawl vessels in 
Chiniak Bay, Kodiak, AK (57°46'N, 152°21'W) during 
late August in 2009. Adults were transported to shore 
and held without food for a 48-hour period at the Kodiak 
Fisheries Research Center (KFRC) to prepare them for 
shipment to the Hatfield Marine Science Center (HMSC) 
in Newport, OR. Fish were placed in 10-L plastic bags 
filled with <500 mL of filtered seawater and saturated 
with pure oxygen, and then packed into chilled cool- 
ers for 24 hours during transport to the HMSC. Upon 
arrival, northern rock sole were transferred to a 3-m 
round holding tank with sand substrate and held under 
a temperature and photoperiod schedule simulating 
conditions in Chiniak Bay. Fish were fed a gelatinized 
combination of herring, capelin, and squid three times 
weekly during the holding period. 
Males and females showed signs of sexual maturation 
starting in February that were similar to reported ma- 
turity schedules for adults sampled near our collection 
sites (Stark and Somerton, 2002). Mature males and 
females were injected with a luteinizing-hormone-re- 
leasing hormone (LNHRa) and strip-spawned 24 hours 
later by gentle squeezing of the abdomen. The gametes 
of ripe males (n- 3) and a female (n- 1) were combined 
in a clean, dry container for a 1-minute period before 
the addition of ambient seawater. Seawater was added 
repeatedly and decanted from the egg batches to rinse 
away excess milt and tissue. 
The use of a single female and multiple males did 
not rule out possible parental contributions to eggs 
that would affect survival between different batches 
of eggs ( sensu Chambers et al., 1989). However, our 
goal was not to determine the range of variation in egg 
characteristics. Rather, the experiment was designed to 
isolate the effects of temperature on the vital rates of 
eggs and larvae. Fertilized eggs were held for a 6-hour 
period at 4°C and gradually adjusted over 24 hours to 
temperature treatments of the experimental apparatus 
to initiate the experiments. 
Egg incubation 
The rearing of northern rock sole eggs was conducted in 
a temperature-controlled, flow-through system consist- 
ing of four temperature treatments: 2°, 5°, 9°, and 12°C. 
Temperature-adjusted seawater was fed to a series of 
seawater baths (i.e., 1x1x0. 5 m square tanks): four rep- 
licates of temperature treatments at 2°, 5°, and 9°C and 
three replicates at 12°C; «=15 total tanks. Temperature- 
controlled seawater was supplied to each of the seawater 
baths at a rate of 2-3 L/min. A 4-L plastic egg incuba- 
tion basket with 220-pm mesh sides and solid bottom 
was placed within each temperature bath. Eggs were 
scattered in a thin layer over the bottom of each basket 
(2 mL of eggs per basket). Based on counts from 2-mL 
egg volumes (n= 5), the number of eggs equaled 1701 ±42 
eggs (mean ±1 standard deviation [SD] ) per egg basket. 
An air stone was placed in each basket to increase water 
flow over eggs during the incubation period. In addition 
to the egg baskets, water baths were outfitted with 1-L 
mesh-bottomed containers to hold newly hatched larvae 
for observation beyond the hatching period. Gently lift- 
ing and lowering containers in the seawater bath twice 
daily achieved seawater exchange within each container. 
Before hatch, 50 eggs were preserved in a 5% buffered 
formalin solution, and measured to the nearest 0.01 mm 
with a dissecting microscope with transmitted light. All 
taxonomic descriptions egg and larval stages were based 
upon individual samples from the 2°C treatment. 
Experimental design 
Egg baskets were checked daily during the course of 
the experiment for any signs of hatch. At the onset of 
hatch, larvae were counted daily and removed from the 
basket, a subsample of which was taken for morphomet- 
ric measurements (n=10-18 larvae). However, to quan- 
tify “hatch quality,” all removed larvae were inspected 
for malformations (i.e., curved or twisted shape) before 
being discarded. Subsampled larvae were anesthetized 
with a 0.0005 ppm solution of tricane methanesulfonate 
(MS-222) for measurement under a dissecting micro- 
scope. The following morphometric measurements were 
recorded: 1) standard length (SL); 2) myotome height at 
the anus (MH); 3) eye diameter (ED); and 4) yolk area. 
Precise length measurements (to the nearest 0.01 mm) 
were obtained with an image analysis system (Image- 
Pro Plus, Media Cybernetics, Bethesda, MD) connected 
to the microscope. Yolk area was determined by using 
the tracing tools of the image analysis software. 
To determine mortality rates of unfed larvae, 100 
larvae were transferred by pipette from each replicate 
egg basket into a corresponding 1-L plastic container 
with mesh bottom. Each 1-L container was suspended 
in a water bath, the temperature of which corresponded 
with that of the incubation baskets. This was done 1-2 
days after the beginning of the hatch cycle to ensure 
