148 
Abstract — Estimation of individual 
egg production (realized fecundity) 
is a key step either to understand 
the stock and recruit relationship 
or to carry out fisheries-independ- 
ent assessment of spawning stock 
biomass using egg production meth- 
ods. Many fish are highly fecund 
and their ovaries may weigh over a 
kilogram; therefore the work time 
can be consuming and require large 
quantities of toxic fixative. Recently 
it has been shown for Atlantic cod 
(Gadus morhua) that image analy- 
sis can automate fecundity determi- 
nation using a power equation that 
links follicles per gram ovary to the 
mean vitellogenic follicular diam- 
eter (the autodiametric method). 
In this article we demonstrate the 
precision of the autodiametric method 
applied to a range of species with dif- 
ferent spawning strategies during 
maturation and spawning. A new 
method using a solid displacement 
pipette to remove quantitative fecun- 
dity samples (25, 50, 100, and 200 mil- 
ligram [mg]) is evaluated, as are the 
underlying assumptions to effectively 
fix and subsample the ovary. Finally, 
we demonstrate the interpretation of 
dispersed formaldehyde-fixed ovarian 
samples (whole mounts) to assess the 
presence of atretic and postovulatory 
follicles to replace labor intensive his- 
tology. These results can be used to 
estimate down regulation (production 
of atretic follicles) of fecundity during 
maturation. 
Manuscript submitted 2 May 2008. 
Manuscript accepted 3 October 2008. 
Fish. Bull. 107:148-164 (2009). 
The views and opinions expressed 
or implied in this article are those 
of the author and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Advances in methods for determining fecundity: 
application of the new methods 
to some marine fishes 
Peter R. Witthames (contact author ) 1 Lorraine N. Greenwood 2 
Anders Thorsen 2 Rosario Dominguez ' 1 
Hilario Murua Maria Korta 3 
Francisco Saborido-Rey 4 Olav S. Kjesbu 2 
Email address for contact author: fecund-fish@tiscali.co.uk. 
1 Centre for Environment, Fisheries & Aquaculture Science (Cefas) 
Lowestoft, Suffolk NR33 OHT, United Kingdom 
Present address: 
Fecund Fish Consultancy 
40 Plumtrees 
Lowestoft, Suffolk NR32 3JH, United Kingdom 
2 Institute of Marine Research (IMR) 
P.O. Box 1870 
Nordnes, N-5817 Bergen, Norway 
3 AZTI Tecnalia Herrera Kaia 
Portualde z/g 20110 Pasaia, Spain 
4 Institute of Marine Research (CSIC) 
Eduardo Cabello 6, 36208, Vigo, Spain 
Research on population fecundity 
(total egg production) has two impor- 
tant applications in the management 
of renewable marine or freshwater fish 
resources. Perhaps the most impor- 
tant is to understand the relationship 
between spawning stock biomass and 
recruitment because it is increasingly 
clear that the assumption of direct pro- 
portionality (Beverton and Holt, 1957) 
is not correct (Marshall et al., 1998; 
Witthames and Marshall, 2008). The 
link between spawning stock biomass 
and recruitment varies according to 
total egg production that in turn is 
dependent, not only on the length fre- 
quency of spawning adults, but also 
on body weight at length (Marshall et 
al., 1998, 1999). In summary the stock 
and recruitment relationship became 
stronger when stock was expressed 
as a product of population length fre- 
quency and fecundity at length (Mar- 
shall et al., 1998). 
A second application for fecundity 
information is to estimate spawn- 
ing stock biomass independently of 
data collected from commercial fish- 
eries (Parker, 1980; Lockwood et al., 
1981; Lo et al., 1992). In addition to 
the fecundity count, information is 
required on a range of parameters 
associated with the development of 
fecundity, such as follicular diameter 
and frequency distribution, spawning 
rates, and individual realized fecun- 
dity, either in one or multiple batches 
shed during one or more spawning 
events. 
In this article we prefer the follow- 
ing definitions for fecundity (Hunter 
et al., 1992). Thus the developing 
fecundity (standing stock of fecun- 
dity referred to as “fecundity” [F] ) 
includes follicles containing cortical 
alveoli (Khoo, 1979) and, in later 
development, yolk granules (Hunter 
et al., 1992) but excludes precursor 
cells such as previtellogenic follicles 
(PVFs) or oogonia. Relative fecundity 
(F bw ) is the fecundity divided by the 
total fish weight. We use the term 
“follicle” to refer to the oocyte and its 
nurturing follicular layers (Tyler and 
Sumpter, 1996) during all phases of 
development from precursor cells to 
residual postovulatory follicles (POFs) 
that indicate previous spawning or 
egg release events. 
The species in this study are of in- 
terest because they represent three 
extremes in spawning strategy (Mu- 
