Sol et a I.: Gonadal development and changes in plasma reproductive steroids in Pleuronectes vetulus 
863 
Table 2 
Length maturation relationship in female English sole collected during months of gonadal recrudescence, October-March. Num- 
bers represent percentage of the animals in the length class at each ovarian stage. 
Length 
(mm) 
Regressed 
Previtellogenic 
Vitellogenic 
Vitellogenic with 
hydrated oocytes 
Spawning 
Spawned out 
n 
<220 
50 
50 
2 
221-230 
100 
1 
231-240 
100 
11 
241-250 
78 
11 
11 
9 
251-260 
69 
15 
15 
13 
261-270 
31 
23 
31 
7.7 
7.7 
13 
271-280 
32 
16 
37 
16 
19 
281-290 
44 
11 
44 
18 
291-300 
25.7 
23 
40 
2.9 
8.6 
35 
301-310 
34 
13 
44 
3.1 
6.3 
32 
311-320 
33 
12 
45 
3 
6.1 
33 
>320 
26.9 
16 
47 
2.9 
7 
11 
172 
o 3 
® (0 
cn c 
cn c 
© 
© — 
CL © 
100 - 
(22) (8) (50) (74) (77) (9) (55) (62) 
£ © 
© o> 
co © 
E w 
.s* 
75- 
m 50“ 
25- 
l 
1 
1 
I 
1 
1 
□ regressed 
^ previtellogenic 
S vitellogenic 
0 
vitellogenic w/ 
hydrated oocytes 
□ spawning 
_ spawned 
* out 
Month of collection 
Figure 2 
Percentage of female English sole at each stage of ovarian devel- 
opment by collection month. Numbers in parentheses represent 
animals sampled each month and histologically analyzed for ova- 
rian stages. 
plasma reproductive steroid concentrations 
(E2: 650 ±110 pg/mL plasma, n= 66; T: 80 ±12 
pg/mL plasma, « =66). Increases in GSI and 
reproductive steroids were observed in ani- 
mals at the previtellogenic stage, and peak 
levels of GSI (20.0 ±4.8, n= 9) and plasma E2 
levels (7000 ±4700, n = 4) were found in 
vitellogenic sole with hydrated oocytes, 
whereas peak plasma T levels (2300 ±620, n= 9) 
were found in spawning females. All reproduc- 
tive parameters were reduced in spawned out 
sole (GSI: 2.8 ±0.5, n=31; E2: 280 ±70, n=21; 
T: 90 ±50, n- 21). 17a, 20(3-P was not detected 
in female sole. 
Figure 5, A-C, shows the mean levels of re- 
productive parameters in female sole at each 
month of collection. The sole sampled in July 
had low GSI (2.14 ±0.45, n= 23) and plasma 
reproductive steroid levels (E2: 710 ±160, 
n= 26; T: 100±30, n=27), which remained low 
until the onset of vitellogenesis (September- 
October for the majority of fish). The highest 
GSI (12.0 ±2.9, n=10) and plasma steroid lev- 
els (E2: 12000 ±5000, n- 3; T: 2400 ±1200, n=4) were 
observed in January. By March, GSI and plasma 
reproductive steroid levels were reduced to levels 
comparable to those found in sole sampled in July. 
In general, fish from Tulalip Bay and Pilot Point had 
similar levels of reproductive parameters, which were 
lower than levels in fish from the University Point. 
The fish at University Point were either in final 
maturation or were actively spawning, whereas fish 
from Tulalip Bay and Pilot Point were migrating to 
spawning areas to undergo final maturation. 
Male Figure 6, A and B, shows the reproductive 
parameters in male sole at each developmental stage. 
The changes in reproductive parameters were simi- 
lar to those observed in female sole. Generally, GSI 
(0.60 ±0.08, n=6) and plasma steroid levels (11KT: 
1900 ±920 pg/mL plasma, n= 4; T: 160 ±60 pg/mL 
plasma, n- 4) were low in regressed animals. In- 
creases in GSI and reproductive steroids were ob- 
served in animals at the early recrudescence stage 
and peaked in spawning fish (GSI: 1.6 ±0.1, n=91; 
11KT: 5300 ±610, n= 57; T: 830 ±130, n=64). Repro- 
