Nichol and Acuna: Annual and batch fecundity of Limanda aspero in the eastern Bering Sea 
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Table 1 
Maturity code criteria for yellowfin sole (Limanda aspera) ovaries based on macroscopic examination. Corresponding histological 
descriptions are included. LP = late perinucleus stage oocyte; PY = partially yolked oocyte; AY = advanced yolked oocyte; MN = oocyte 
with migratory nucleus; HY = unovulated hydrated oocyte. POFs = postovulatory follicles. PY is defined as an oocyte with yolk 
globules that filled less than half the volume of the oocyte. 
Maturity 
code 
Condition 
Macroscopic examination 
Histological examination 
1 
immature 
Ovary clear to slightly pink or grey-pink. No dis- 
tinct oocytes. Ovarian wall thin and taut around 
ovary interior. 
LP is the most advanced oocyte stage. Ovarian wall 
diameter thin (generally <2 pm). 
2 
maturing 
Ovary usually opaque with distinct vitellogenic 
oocytes. A network of veins covers the ovary. 
PY or AY oocytes present (yolk globules present). MN 
oocytes may be present. POF may be present. 
3 
hydrated 
As in code 2, but some portion of oocytes are trans- 
lucent (hydrated-unovulated). Hydrated oocytes 
are larger than the opaque oocytes and are ran- 
domly scattered about the ovary. 
HY oocytes (yolk coalesced) present, each surrounded 
by a follicle. AY oocytes present if prior to last batch. 
MN oocytes usually present if prior to last batch. POF 
may be present. 
4 
spawning 
Hydrated (translucent) oocytes in lumen of ovary 
(ovulated). A continuous band of hydrated oocytes 
may also be visible from the ovary sides. Eggs 
may run with slight pressure. If all oocytes are 
translucent, they represent the last batch of eggs 
to be spawned in the season. 
Ova present. AY oocytes present if prior to last batch. 
POFs present. MN oocytes usually present if prior to 
last batch. 
5 
spent 
Deflated ovary, often with blood. Ovary wall thick 
and often flaccid around ovary interior. 
LP to PY oocytes present. Ovarian wall diameter thick 
(generally >3 pm). 
numbers of HY oocytes in the respective subsample. Ovaries 
were categorized by stages in the batch spawning succes- 
sion: a first batch was recognized by the presence of HY and 
AY oocytes, and absence of POFs. A middle batch was recog- 
nized by the presence of HY oocytes, AY oocytes, and POFs. 
A final batch was recognized by the presence of HY oocytes 
and the absence of remaining AY or MN oocytes. 
Fecundity-total length relationships were computed for 
total and batch fecundity by using Gauss-Newton nonlinear 
least squares regression (SAS Institute, 1989). The num- 
ber of batches spawned from a female for a given fish 
length was then estimated as the estimated total fecun- 
dity divided by the estimated batch fecundity. 
Results 
Histological evaluation 
Histological evaluation of 767 ovary pairs, in most cases 
(93%), verified the general ovary codes that were assigned 
macroscopically (Table 1). Resulting groupings are shown 
in Table 2. We note here that maturing (maturity-code 
2) ovaries included females that had spawned one or 
more batches (POF present) but contained no hydrated 
oocytes (HY) or ova; these ovaries were indistinguishable 
macroscopically from advancing ovaries that had not yet 
spawned a batch. Early perinucleus stage oocytes were 
present in all ovaries examined. Late perinucleus stage 
oocytes were present in all but one of the mature fish ova- 
ries (??=665; maturity-codes 2-5). 
Migratory nucleus stage (MN) oocytes, vitellogenic oo- 
cytes that are precursors to hydrated oocytes, were pres- 
ent in 96% of the females undergoing oocyte hydration and 
91% of spawning females. The high occurrence of MN oo- 
cytes among fish about to spawn a batch suggests that fish 
do not wait extended periods between batch spawnings. 
Postovulatory follicles were observed in 121 of the ova- 
ries examined. POFs were present in 50 of 75 females un- 
dergoing hydration, indicating for these fish that at least 
one batch was previously spawned. For the other 25 fe- 
males with hydrated ovaries containing no POFs, HY oo- 
cytes represented the first batch of a series of batches. We 
could not distinguish more than one apparent age of POF 
among the 50 fish that had begun spawning. This indicates 
that yellowfin sole either resorb POFs before a succeeding 
batch is ovulated or that POFs of different ages (from dif- 
ferent batches) are present but are indistinguishable. 
Evidence of more than one series of batdi 
spawnings 
A total of 16 females with maturing ovaries (maturity- 
code 2) contained residual chorion tissue within the ovary 
lumen (Table 2; Fig. 2). The chorion tissue in these 
cases was sufficiently large to conclude that they were 
unspawned ova from a previous spawning. The ovaries 
ranged from those in early stages of yolk accumulation 
