236 
Fishery Bulletin 95(2), 1 997 
Table 1 
Results of multiple regression analysis examining effects of biological factors (length, age, GSI, sampling year, and sampling time 
in Julian day) on egg weight and fecundity. Factors that did not contribute significantly to the model are not included in the table. 
Regression results 
Model variables 
df 
F-test 
r 2 
t-value 
p -value 
Fecundity 
Overall model 
98 
42.25 
0.63 
— 
<0.0001 
length 
0.48 
8.31 
<0.0001 
+GSI 
0.56 
5.98 
<0.0001 
+sampling time 
0.59 
-3.41 
0.0010 
+age 
0.63 
-3.13 
0.0023 
Egg weight 
Overall model 
98 
154.23 
0.76 
— 
<0.0001 
GSI 
0.73 
8.674 
<0.0001 
+sampling time 
0.76 
3.164 
0.0004 
lated primarily to the degree of gonadal development 
(i.e. GSI), and increased as vitellogenesis progressed. 
In vitellogenic sole sampled in December, mean egg 
weight was 4.6 ± 0.4 pg (n=66), whereas in January, 
it was 13.0 ± 0.9 pg (n=34) (P<0.0001, 1-way ANOVA). 
In multiple regression analysis, the best predictors 
of egg weight were GSI (73% of variation) and sam- 
pling time (3% of variation), both of which were posi- 
tively correlated with egg weight (Table 1). 
Because of their strong influence on fecundity and 
egg size and because of their high degree of individual 
variability, the basic parameters included in Table 1 
were adjusted for in subsequent analyses to assess 
the effects of contaminant exposure, nutritional fac- 
tors, and site of capture on fecundity and egg size. 
Site-specific patterns of egg production 
Mean fecundity, relative fecundity, egg weight, and 
reproductive output for English sole from Port Su- 
san, Sinclair Inlet, the Duwamish Waterway, and 
Eagle Harbor are shown in Table 2, along with re- 
sults of 2- way ANOVA examining the effects of site 
and sampling time on these parameters. Overall, 
fecundity did not change significantly with sampling 
time, and no significant site-month interactions were 
seen for fish from Port Susan, the Duwamish Water- 
way, or Eagle Harbor. Fish from Sinclair Inlet, how- 
ever, had significantly higher fecundity in Decem- 
ber than in January (£=2.613, P=0.0105). Site of cap- 
ture had a significant effect on fecundity; fish from 
the Duwamish Waterway exhibited higher fecundity 
than fish from the Port Susan reference site (£=2.016, 
P=Q.0467). Like fecundity, relative fecundity did not 
show any consistent overall change with sampling 
time, but significant site-month interactions were 
seen for fish from Sinclair Inlet, Port Susan, and 
Eagle Harbor. Relative fecundity of fish from Sinclair 
Inlet was significantly higher in the December than 
in the January sampling (£=2.829, P=0.0058), 
whereas in fish from Eagle Harbor (£=-2.747, 
P=0.0072) and Port Susan (£=-4.232, P=0.0001), rela- 
tive fecundity was significantly lower in December 
than in January. There was also a significant effect 
of site on relative fecundity, which was lower in 
Sinclair Inlet than in Port Susan sole (£ =-3.46, 
P=0.0006). 
Egg weight increased significantly, by 2- to 3-fold, 
between December and January at all sampling sites. 
No significant site-month interactions were seen. Site 
of capture did not have a significant effect on egg 
weight, although Duwamish Waterway fish tended 
to exhibit lower egg weights than fish from Port Su- 
san (£ =-1.878, P=0.0635). Like egg weight, repro- 
ductive rate was significantly higher in January than 
in December. However, no significant intersite dif- 
ferences or month-site interactions were seen for re- 
productive rate. 
The effects of site of capture on egg weight and 
fecundity were also evaluated by using multiple re- 
gression, after adjusting for the influence of fish 
length, age, GSI, and sampling time (see Table 1). 
Results showed that even after fish length, sampling 
time, and GSI had been accounted for, Duwamish 
Waterway fish had significantly higher fecundity 
(£=4.52, P=0.0001) than comparable animals from the 
Port Susan reference site (see Fig. 2A). Age and fe- 
cundity relationships were also analyzed by using 
multiple regression (excluding fish length from the 
model); the results showed that Duwamish Water- 
