Rodgveller et at: Effects of maternal age and size on embryonic energy reserves and developmental timing of Sebastes ma/iger 
37 
gravid females in the laboratory 
has the potential to introduce 
laboratory effects on oil globule 
size at parturition and also on 
parturition date. For example, 
some yellowtail rockfish (S. fla- 
vidus) resorbed embryos when 
in the laboratory (Eldridge et 
ah, 2002). Laboratory results 
may also be skewed because 
larval performance in the labo- 
ratory environment may differ 
from performance in the natu- 
ral environment (Marshall and 
Keough 2008; Marshall et al., 
2010). Sampling gravid fish in 
the field and taking immediate 
measurements excludes poten- 
tial effects of laboratory rearing. 
Because embryos among females 
will be at different developmen- 
tal stages, the relationship be- 
tween the stage of embryos and 
preparturition larvae (embryos 
that hatch in the ovary shortly 
before parturition) and oil glob- 
ule size must be accounted for 
when assessing maternal effects 
on oil globule size. 
Our objectives were to assess 
the effects of maternal size and 
age on 1) the oil globule size of 
embryos and preparturition larvae 
of quillback rockfish sampled op- 
portunistically in Southeast Alas- 
ka; 2) the developmental stage of 
embryos; and 3) fecundity. 
Materials and methods 
Field sampling and oil globule 
measurements 
136°0’0"W 135°0'0"W 134WW 133WW 132°0'( 
59°0'0"N 
58WN- 
57°0'0"N- 
-58°0'0"N 
•57°0'0"N 
Pacific Ocean 
■se-o'CTN 
0 15 30 60 Kilometers 
1 i i i I i i_ 
1 1 
138WW 137WW 
136WW 
135WW 
134°0'0"W 
Figure 1 
Map of study areas in Southeast Alaska where quillback rockfish ( Sebastes 
maliger) were sampled in 2006-08. 
Gravid quillback rockfish were 
sampled opportunistically with hook-and-line gear in 
Southeast Alaska during April or May, 2006-2008 (Fig. 
1). Fish were sampled in Cross Sound on the northwest 
side of Chichagof Island during 15-20 April 2006, 
14-19 April 2007, and 22-26 April 2008. Additional 
sampling occurred on the southeast side of Baranof 
Island near the National Oceanic and Atmospheric 
Administration’s Little Port Walter research station 
during 31 May 2007 and 2-5 May 2008. Although each 
sampling trip occurred over several continuous days, 
for simplicity we will refer to each trip as a “sampling 
period.” At both locations, gravid females were cap- 
tured at depths ranging from 30 to 75 m (98-246 ft). 
Gravid females were weighed (nearest 1.0 g) and 
measured (total length, nearest 1.0 cm), and otoliths 
were collected. Otoliths were aged with the break-and- 
burn technique (MacLellan, 1997) by scientists within 
the Alaska Fisheries Science Center’s Age and Growth 
Program. Because oil globule size is closely related to 
energy stores, the oil globule diameter (OGD) was used 
as a proxy for the amount of stored energy, which is 
used by embryos and larvae during early development 
and after they enter the marine environment before 
they learn to feed. Twenty embryo or preparturition 
larva samples were collected from each female by mix- 
ing all embryos from an ovary in a dish and randomly 
subsampling 20 embryos or preparturition larvae for 
oil globule measurements. Previous analyses showed 
that a coefficient of variation of less than 5% for aver- 
age oil globule diameter for a female was possible with 
a sample size of 20. 
All subsampled embryos were photographed by using 
a dissecting microscope soon after capture in the field. 
