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Fishery Bulletin 107(2) 
sole Limanda asper (Nichol and Acuna, 2001) and Eu- 
ropean plaice (Kennedy et al., 2007). Samples used for 
the auto- diametric calibration and in subsequent deter- 
mination of F ow should have the same fixation history 
because fixing conditions affect Dp F ow , and circularity 
and also affects the ovarian weight (Klibansky and 
Juanes, 2007) used to raise F ow to fecundity. 
We would not recommend the general use of PAS stain 
for image analysis in mature fish because it obscures 
< 300 
400 500 600 700 800 
o> 
600 800 1000 1200 
300 400 500 600 700 800 900 
Mean follicle diameter (pm) 
Figure 6 
Reduction in relative fecundity (F bw ) during 
maturation, measured as mean follicle diam- 
eter (Dp pm) in Atlantic cod ( Gadus morhua ), 
European plaice (Pleuronectes platessa), and 
common sole (Solea solea) (A-C, respectively) 
collected from the Irish Sea during 1995. The 
equation for the fitted line and regression coef- 
ficients are shown in Table 4. 
the chorion detail which is used to classify atretic from 
normal vitellogenic follicles (Kjesbu et al., 1991). The 
main advantages of PAS, compared to the other stains 
evaluated, was that it was the most color fast, worked 
with all the species where it was tried, and provided 
specific staining to color more transparent objects such 
as cortical alveoli, hydrated, and postovulatory follicles. 
It is however more laborious to apply, but has been suc- 
cessful in all applications where it has been tried previ- 
ously (Kennedy et al., 2007) and performed well in the 
comparison of manual versus automatic measurements. 
Similar results have also been found for nonstained fol- 
licles, although not reported in the results section. 
Based on our results and earlier reports (Witthames 
and Greer-Walker, 1995; Kurita et al., 2003; Thorsen 
et al., 2006; Kennedy et al., 2007) fecundity is down 
regulated by the production of atretic follicles during 
maturation. If samples are taken close to spawning 
season, down regulation is not significant (Oskarsson 
and Taggart, 2006), but the timing of sampling should 
be considered especially when studying multiyear col- 
lections for example: Atlantic cod (McIntyre and Hutch- 
ings, 2003), European plaice (Horwood et al., 1986; 
Rijnsdorp, 1991) and common sole (Witthames et al., 
1995). Using the autodiametric method, it was pos- 
sible to predict Dp providing data on ovarian weight 
and fecundity is reported using a rearranged Equa- 
tion 4. This method was used in this study for 1995 
survey data to standardize fecundity for maturity and 
indicated that the spawning stock biomass of Atlantic 
cod, European plaice, and common sole may have been 
overestimated by about 12% based on follicle diameters 
of 650, 1100, and 600 pm, respectively. Although we 
consider that follicular atresia was an important cause 
of negative fecundity residuals in this study, we do not 
exclude an alternative explanation that more fecund 
individuals within a fecundity sample produce smaller 
eggs, and vice versa (i.e., a trade off between fecundity 
and egg size). Such a trade off is likely in a comparison 
between stocks such as Atlantic herring (Winters et al., 
1993) but has not, to our knowledge, been proven to oc- 
cur within one stock. One report referring to Atlantic 
cod from the Norwegian coast (Kjesbu et al., 1996a) 
indicates that much of the variability in egg size occurs 
during the final maturation rather than variability in 
follicular size when final maturation occurs. Overall 
our view is that the relationship used for fecundity 
standardisation should be documented, including the 
follicle size reference point along with the unadjusted 
results. 
Different image analysis configurations used by four 
institutes to collect the autodiametric calibration data 
produced a low CV of fecundity estimates for new pre- 
dictions. The data can be accumulated without inter- 
vention (Thorsen and Kjesbu, 2001) in automatic mode 
and has utility for a number of species. Since it is an 
automatic process it is important that all follicular 
classes of interest are measured with equal selectivity, 
including cortical alveoli, atretic, or hydrated follicles. 
We suspect that the cause of the higher fecundity CV 
