859 
Gonadal development and associated 
changes in plasma reproductive 
steroids in English sole, 
Pleuronectes vetulus, 
from Puget Sound, Washington 
Abstract .—Gonadal development, 
and associated changes in reproductive 
parameters were investigated in adult 
female and male English sole (Pleuro- 
nectes vetulus) in Puget Sound to pro- 
vide baseline data for future research 
on effects of contaminants on reproduc- 
tive endocrine function in this species. 
Changes in gonadal histology, gonado- 
somatic index (GSI), and plasma repro- 
ductive steroids (female: 17|3-estradiol 
[E2], testosterone [T] ; male: T, 11- 
ketotestosterone [ 1 1KT] ) were moni- 
tored throughout the spawning season. 
Female sole sampled July through 
early September were primarily re- 
gressed or previtellogenic and had low 
GSI and plasma steroid levels. GSI and 
plasma steroid levels were also low in 
male sole sampled during this time, but 
the majority had already entered sper- 
matogenesis and, in some fish, produc- 
tion of mature sperm was observed. 
Fish sampled in October were in the 
early stages of vitellogenesis and sper- 
miogenesis and showed increases in 
GSI and plasma steroid levels. By No- 
vember, about 50% of female fish had 
entered vitellogenesis and about 30% 
of males were producing sperm. Propor- 
tions of vitellogenic females and sperm- 
producing males continued to increase 
through January, with significant num- 
bers of spawning females and males 
present in February. By late March, the 
majority of both sexes were spent. 
Vitellogenic female sole had the high- 
est plasma E2 levels, vitellogenic sole 
with hydrated oocytes had the highest 
GSI, and spawning female sole had the 
highest plasma T levels. Plasma T, 
11KT, and GSI were highest in spawn- 
ing male sole. Reproductive parameters 
returned to baseline levels in spawned 
out female and male sole. A potent 
maturation-inducing steroid (MIS) in 
many species of teleosts, 17a, 20(3- 
dihydroxy-4-pregnen-3-one, was not 
detected in spawning English sole. Ad- 
ditional research is needed to identify 
the MIS in English sole and to under- 
stand better the hormonal regulation of 
early gonadal development in male sole. 
Manuscript accepted 28 January 1998. 
Fish. Bull. 96:859-870 (1998). 
Sean Y. Sol 
O. Paul Olson 
Daniel R Lomax 
Lyndal L. Johnson 
Environmental Conservation Division 
Northwest Fisheries Science Center 
National Marine Fisheries Service, NOAA 
2725 Montlake Boulevard East 
Seattle, Washington 98112 
E-mail address (for S. Y. Sol): Sean.Sol@noaa.gov 
English sole (Pleuronectes vetulus) 
is a commercially important flatfish 
species indigenous to the west coast 
of North America. It is also a pri- 
mary sentinel species for a number 
of environmental monitoring pro- 
grams on the west coast of the 
United States, including the Na- 
tional Benthic Surveillance Project 
(Myers et ah, 1994) and the Puget 
Sound Ambient Monitoring Pro- 
gram (PSWQA 1 ). Studies suggest 
that female English sole are quite 
sensitive to environmental contami- 
nants. For example, female sole 
from several sites within Puget 
Sound, WA, with high levels of poly- 
chlorinated biphenyls (PCBs) and 
polycyclic aromatic hydrocarbons 
(PAHs) (in sediment), exhibit vari- 
ous types of reproductive dysfunc- 
tion, including depressed sex hor- 
mone levels, altered or inhibited re- 
productive development, and re- 
duced egg and larval viability 
(Johnson et al., 1988, 1993; Casillas 
et ah, 1991; Collier et ah, in press). 
Male English sole may also be at 
risk for reproductive injury. Recent 
studies suggest that exposure to 
certain chemical compounds (e.g. 
alkylphenols, phthalates, and some 
PCBs and chlorinated pesticides) 
can reduce testicular growth and 
sperm production in male teleosts 
(Jobling et ah, 1996; Nimrod and 
Benson, 1996), and alterations in 
reproductive steroids have been re- 
ported in male fish exposed to oil 
and other pollutants (Truscott et ah, 
1992a; Idler et ah, 1995). However, 
no comprehensive studies have 
been conducted on the effects of en- 
vironmental contaminants on re- 
productive function in male English 
sole. Before such studies can be car- 
ried out effectively, the normal re- 
productive endocrine cycle of male 
English sole must be characterized. 
The general life history of English 
sole is well known (Ketchen, 1947; 
Harry, 1959; Garrison and Miller, 
1982), and its cycle of oocyte devel- 
opment and related changes in es- 
tradiol-17p (E2) and other plasma 
parameters have been described 
1 PSWQA (Puget Sound Water Quality Au- 
thority). 1995. 1994 Puget Sound up- 
date: fifth annual report of the Puget 
Sound Ambient Monitoring Program. 
Puget Sound Water Quality Authority, 
Olympia, WA, 122 p. 
