Johnson et a I : Fecundity and egg weight in Pleuronectes vetulus 
245 
in serum triglycerides have also been observed in 
previous studies. For example, English sole showed 
increased serum triglyceride levels in response to 
laboratory exposure to model toxicants bromo- 
benzene and o-bromophenol (Casillas and Myers, 
1989). Consequently, elevated levels of these param- 
eters in Duwamish Waterway fish could be a reflec- 
tion of toxicant exposure rather than good nutritional 
status. Moreover, the contaminants may affect fecun- 
dity or egg size indirectly through their impact on 
liver function, lipid disposition, or lipid metabolism. 
Results of this study suggest the possibility of such 
interactive effects of contaminants and nutritional 
factors on egg development. 
In addition to PCB’s and PAH’s, other contami- 
nants, such as heavy metals and organotins, which 
are present in the Duwamish Waterway and to a 
lesser extent at Sinclair Inlet (Krone et al., 1989; 
PSWQA, 1994; Dutch et al. 2 ), could affect egg weight 
or other aspects of gonadal development in English 
sole. Previous studies have shown that a number of 
toxic trace elements, including copper, lead, mercury, 
and cadmium (Kaviraj, 1983; Munkittrick and Dixon, 
1988; Dethlefson, 1989), as well as tributyl tin (TBT) 
(Walker et al., 1990), can affect egg size or gonadal de- 
velopment in fish. Previously, Krone et al. (1989) 
showed increased tissue concentrations of TBT in En- 
glish sole from the Duwamish Waterway. However, 
many of these trace elements in their organic form do 
not bioaccumulate in English sole (Meador et al., 1994) 
and indicate low bioavailability. 
Increased egg production or production of more but 
smaller eggs is not the most commonly observed re- 
sponse in fish exposed to environmental contami- 
nants, but such trends have been observed in some 
previous studies. Slooff and DeZwart ( 1983) reported 
increased fecundity in bream exposed to a mixture 
of chlorinated and aromatic compounds in the Rhine 
River, and Walker et al. (1990) reported a similar 
finding for medaka exposed to TBT. Reduced egg size, 
although not necessarily in conjunction with in- 
creased egg production, has been reported in a num- 
ber of studies in which fish were exposed to PAH’s, 
PCB’s, orboth(Kime, 1995). Interestingly, since 1900, 
North sea plaice have also exhibited a trend toward 
production of more but smaller eggs (Rijnsdorp, 
1991). The causes of these changes are unknown, but 
it is suspected that they are most likely related to 
changes in environmental conditions, which could 
2 Dutch, M., H. Dietrich, and P. L. Striplin. 1993. Puget Sound 
Ambient Monitoring Program 1992: marine sediment monitor- 
ing task — annual report 1992. Environmental Investigations 
and Laboratory Services Program, Washington State Dep. Ecol- 
ogy, Olympia, WA. Publ. 93-87. 
include environmental degradation associated with 
anthropogenic activities. 
In summary, the results of this study suggest that 
egg weight and number in English sole are influenced 
by a variety of factors, including exposure to organic 
chemical contaminants such as PCB’s and PAH’s, 
nutritional status, and growth rate. Although chemi- 
cal contaminant exposure did not appear to have a 
major impact on egg development in English sole, 
high concentrations of contaminants in tissues or 
body fluids showed significant associations with cer- 
tain potentially detrimental changes: elevated PCB 
concentrations in liver were correlated with reduced 
plasma vitellogenin levels and reduced egg weight, 
and high levels of biliary FAC’s were associated with 
increased ovarian atresia and reduced fecundity. The 
impact of these alterations in egg weight and num- 
ber on the reproductive fitness of affected fish is not 
clear. It is likely that smaller eggs will tend to pro- 
duce smaller larvae, and reduced larval size has been 
associated with lower growth and survival rates in 
other flatfish species (Buckley et al., 1991). However, 
the detrimental effects of reduced egg weight could 
be offset by increased egg production, or, at least in 
the case of the Duwamish Waterway fish, by a rela- 
tively fast growth rate and high age-specific fecun- 
dity. In order to gain a better understanding of the 
relationships between chemical contaminants, nu- 
tritional factors, and alterations in gonadal develop- 
ment and egg production, we are currently investi- 
gating the effects of PCB’s, AH’s, and food supply on 
egg weight and fecundity in further laboratory stud- 
ies with English sole. 
Acknowledgments 
We thank Sue Pierce and other members of the En- 
vironmental Chemistry Branch, Environmental Con- 
servation Division, for assistance in measurement 
and calculation of PCB concentrations in tissue 
samples; William Gronlund, Paul Plesha, and 
Herbert Sanborn for assistance in fish collection; 
Mark Myers and Paul Olson for assistance in histo- 
logical examination of liver and ovary tissue; Tom 
Horn and Sylvester Spencer for measurement of bil- 
iary FAC’s; Ethel Blood for measurement of plasma 
triglyceride and glucose concentrations; and Herbert 
Sanborn, Casimir Rice, Tracy Collier, and two anony- 
mous referees for reviewing the manuscript. 
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