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Fishery Bulletin 96(4), 1998 
vitellogenic sole compared with regressed sole, and 
highest plasma T concentrations were observed in 
spawning sole. Similar observations have been made 
in winter flounder (Pleuronectes americanus), where 
concentrations of T have been correlated with oocyte 
stages characterized by germinal vesicle migration 
(Truscott et al., 1992b). In salmonids, estrogens and 
androgens such as T appear to play an important 
role in regulating production of pituitary GTH-II 
(Xiong et al., 1993, 1994), which stimulates the pro- 
duction of progestins, steroids involved in inducing 
final maturation (Swanson, 1991). This would be con- 
sistent with the high concentrations of T observed in 
spawning female English sole and winter flounder. 
In male teleosts, 11KT is known to be important 
in stimulating spermatogenesis, whereas T is known 
to be important in feedback effects on the pituitary 
(Borg, 1994). T is a biosynthetic precursor to 11KT 
(Ozon, 1972). As with E2 in female sole, the levels 
of T and 11KT covaried in male sole; 11KT levels 
were significantly higher than T levels at all stages 
of gonadal development. Similar relations between 
T and 11KT concentrations have been observed in 
other flatfish species, such as Pacific halibut 
(Hippoglossus stenolepis) (Liu et al., 1991) and 
winter flounder (Harmin et al., 1995). These re- 
sults are consistent with the role of 11-oxygenated 
androgens as the dominant regulatory androgens 
in male teleosts, stimulating secondary sexual 
characters, reproductive behavior, and spermato- 
genesis (Borg, 1994). 
In male winter flounder (Harmin et al., 1995) 
and plaice (Wingfield and Grimm, 1977), repro- 
ductive parameters (GSI, plasma 11KT and T con- 
centrations) increased with the onset of seasonal 
testicular recrudescence, reached a peak in 
prespawning and spawning males, then decreased 
in spawned out males. However, in most male te- 
leosts that have been studied, the levels of plasma 
11KT and T peak during the prespawning period 
rather than during the spawning period (Borg, 
1994). For example, the levels of plasma 11KT and 
T in Atlantic halibut (Hippoglossus hippoglossus) 
peaked briefly in sperm-producing fish, then de- 
clined during the spawning period (Methven and 
Crim, 1991). The reproductive parameters mea- 
sured in male English sole were similar to the 
patterns observed in winter flounder and plaice, 
where steroid concentrations remained high dur- 
ing the peak spawning period. 
Interestingly, the reproductive steroid levels 
observed in spawned out male English sole were 
significantly lower than levels observed in re- 
gressed males that were collected in summer and 
early fall. A pattern somewhat like this was also 
observed in male winter flounder and Atlantic 
halibut. In both male winter flounder (Harmin et 
al., 1995) and Atlantic halibut (Methven and Crim, 
1991), the plasma steroid levels were low in spent 
males but began to increase about two months af- 
ter the peak spawning period. Although this study 
did not measure reproductive parameters in the 
months immediately following the peak spawning 
period (i.e. April through June), similar changes 
