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Fishery Bulletin 107(2) 
exhibiting a bimodal frequency distribution, but in 
each case the autodiametric calibration made it possi- 
ble to make estimates of F ow with an acceptable level 
of precision. Equation 5 gave a small but significant 
(PcO.OOOl) improved fit, but only for Atlantic cod with 
hydrated follicles, and reduced the CV of F ow esti- 
mates predicted from 450 to 1050 pm D,. The overall 
precision after inserting an ascending series of D f in 
Equations 4 and 5, spanning the range found in each 
species was always better than a CV of 3% based on 
a prediction for new data. 
A combination of the data in a general calibration 
curve (Fig.9A) is provided to show that the auto-dia- 
metric method has general application and may be used 
with other species. However when compared against the 
individual species model there was difference in the pre- 
dictions by up to 20% both within species and between 
institutes (Table 6). The variance was greater in the 
fish with a continuous follicular distribution, especially 
in the case of European hake (Fig. 9, B and C). 
Discussion 
Our results show that the pipette method for 
sampling fresh ovaries at sea can be used to 
replace the need to return the whole ovary for 
the gravimetric fecundity method (Bagenal and 
Braum, 1968), provided ovarian weight can 
be recorded precisely onboard. Although the 
pipette fecundity was slightly lower (94.7%) 
compared to the gravimetric fecundity, we 
feel that the scale of difference can be easily 
nullified by a small correction factor and is 
small compared to the reported variability in 
fecundity over time (Rijnsdorp, 1991) and space 
(Witthames et al., 1995). Our confidence in 
making this statement is increased because of 
a direct comparison between both methods for 
the same ovary and because the autodiametric 
calibrations are very similar without large 
residuals attached to either method. A previ- 
ous report described a cut down plastic syringe 
to suck up standard sized ovarian samples of 
1.54 g (CV=3.7 rc=155), but the commercially 
available alternative described in this paper 
has two advantages: 1) it is already calibrated 
for a range of sample sizes (25, 50, 100, and 
200 pL), and 2) it is suited to taking small 
samples appropriate for fecundity determina- 
tion in species such as Atlantic mackerel and 
European hake. In our results ovarian weight 
showed on average a small decline (-5%) from 
fresh to fixed weight for each species which 
was considerably different from a previous 
report (Klibansky and Juanes, 2007) at +5% 
or less. The reasons for the difference are not 
apparent but do not involve the ratio of fixative 
to weight of ovarian tissue because the range 
used in this work (1.7 to 9.1 times NBF to ovar- 
ian weight) spans the ratio of four times where 
a positive weight change was recorded. 
Collection of fecundity samples in this 
way has clear advantages: 1) require small 
amounts (1.2 compared to more than 5000 ml 
for species like Atlantic cod) of NBF (classed 
as a carcinogen), 2) reduced exposure because 
of the smaller free surface for evaporation, 3) 
lower environmental impact for disposal of 
fixed tissue and waste fixative, 4) it is more 
feasible to collect fecundity samples on com- 
Figure 3 
Appearances of atretic oocytes taken from 2 year old aquaculture 
reared Atlantic cod ( Gadus morhua) at Institute IMR in 2004. 
(A) Image taken from an unstained whole mount prepared from 
an ovary biopsy containing high levels of alpha atretic follicles 
(dashed circles), beta atretic follicles (dotted circles), and normal 
vitellogenic follicles (black circles). (B) Histological section of the 
biopsy in A showing the same classes of follicle (outlined using 
the same line key as A) after processing into histological section. 
In each case arrows point to the disintegrating chorion used for 
classification of alpha atretic follicles. The scale bars (top left of 
A and B) = 500 pm. 
