150 
Fishery Bulletin 107(2) 
Table 1 
Details of the collection date, source, and maturity stage of wild fish (Atlantic cod [Gadus morhua ], haddock [Melanogrammus 
aeglefinus], European hake [Merluccius merluccius], Atlantic herring [Clupea harengus], Atlantic mackerel [Scomber scotnbrus], 
European plaice [Pleuronectes platessa ], common sole [Solea solea], redfish (deep water redfish [Sebastes mentella ] or golden 
redfish [Sebastes marinus]) used in the study. The samples where taken from commercial or research vessel catches. Collections 
made in 1995 were used for the study of fecundity down regulation and the later collections from 1998 onward for the study of 
fecundity methods. 
Atlantic 
Cod 
Haddock 
European 
hake 
Atlantic 
herring 
Atlantic 
mackerel 
European 
plaice 
Common 
sole 
Redfish 
Date 
Jan-Mar 1995, 
2003-04, 2007 
Feb 2007 
Mar 2003 
Jan 1998 
Mar 2004 
Jan-Mar 1995, 
2000, 2007 
Jan-Feb 
1995 
Sep-Nov 
2000-2001 
Source 
Lofoten 
Andenes 
Norway 
North and 
Irish Sea 
Irish Sea 
Galicia 
Biscay 
Celtic Sea 
Norwegian- 
spring 
spawning 
stock 
Western 
Atlantic 
stock 
Irish Sea 
Irish Sea 
Iceland 
Irminger 
Sea 
Maturity 
stage 
Prespawning 
and spawning 
Pre- 
spawning 
Pre- 
spawning 
Pre- 
spawning 
Pre- 
spawning 
Pre- 
spawning 
Pre- 
spawning 
Pre- 
spawning 
and to near 
spawning spent 
cod, European plaice, and common sole ( Solea solea) 
and the implications for estimating total fecundity prior 
to the start of spawning. 
Materials and methods 
Ovarian sampling, follicle measurement equipment, 
and homogeneity 
Ovarian samples were collected by the four institutes 
working on two or more of the following species Atlantic 
cod, Atlantic herring, European hake, Atlantic mackerel, 
European plaice, and redfish (including deep water 
redfish and golden redfish) for studies unrelated to this 
paper (Table 1). Biological information was taken from 
each fish, but only the information related to this method 
development (ovarian mass and maturity stage) is used 
here. Only active ovaries (Hunter et al., 1992) were 
selected and weighed to better than 2% of their mass, 
either with a motion-compensated balance (POLS Elec- 
tronics, Isafjordur, Iceland) when sampled at sea or with 
a standard balance when on shore. Fish that contained 
many ovulated eggs (caught in the act of spawning) were 
not used in the autodiametric calibration because they 
show a heterogeneous distribution (Witthames, 2003). 
In each case ovaries or ovarian subsamples were fixed 
in a minimum of two volumes of NBF for a minimum 
of 14 days. Quantitative subsamples were taken by one 
of two methods: 1) from the fresh unfixed ovary (Atlan- 
tic cod, Atlantic mackerel) immediately after capture 
at sea using a Wiretrol II pipette (Drummond Scien- 
tific, Broomall, PA), or 2) from the fixed ovary in the 
laboratory with a scalpel (Atlantic cod, European hake, 
European plaice, and redfish). The Wiretrol II pipette 
consists of a Teflon-tipped stainless steel piston within a 
graduated glass tube with a 1 or 2 millimetre (mm) bore 
that can remove 26 and 54, or 106 and 212 milligrams 
(mg), respectively, of tissue when inserted through the 
ovarian tunica. 
Image analysis hardware and software, including the 
camera resolution and light intensities used by each 
institute to measure follicular diameter and circularity, 
varied (Table 2). The follicle data were analyzed with 
Microsoft Excel to calculate follicular mean, standard 
deviation, and leading cohort (Lc) (defined as the mean 
of largest 10% of follicles measured). PVFs were exclud- 
ed from the fecundity count and frequency distribution 
based on a minimum follicular diameter of 150 and 250 
pm in European hake, and Atlantic cod, respectively 
(Kjesbu, 1991; Murua and Motos, 2006). In the case of 
Atlantic mackerel there were no published data avail- 
able, so a diameter of 185 pm was used based on our 
observation of the smallest follicles containing cortical 
alveoli and a publication focusing on Atlantic mackerel 
fecundity determinacy (Greer-Walker et al., 1994). In 
all other species, where the follicular frequency was 
not continuous, only dark yolk-bearing follicles in the 
leading mode were included in the fecundity count. Fol- 
licles were disaggregated from the ovarian sample by 
sucking them in and out of a Pasteur pipette (Thorsen 
and Kjesbu, 2001) prior to spreading them out in a 
counting chamber as a single layer completely covered 
by water. If small clumps of follicles remained they were 
measured manually as discrete follicles, whereas larger 
clumps were separated and exposed to more pressure 
washing by the pipette or a garden spray (Institutes A 
and C). All the follicles were counted in the subsam- 
ples but the method for collecting the follicular meas- 
urements differed according to each institute’s image 
