Colmenero et al.: Reproductive strategy of Lophius piscatorius in Mediterranean waters 
69 
Table I 
Oocyte diameters, ranges and means with standard errors (SEs), and histological characteristics of ovarian follicles in white 
anglerfish {Lophius piscatorius), collected from the northwestern Mediterranean Sea between June 2007 and December 2010. 
SE=standard error, at each stage of oocyte development. 
Stages of 
Mean oocyte 
Oocyte diameter 
oocyte development 
diameter (pm) (SE) 
(pm) range 
Histological characteristics 
Primary growth stage 
82.79 (2.34) 
12-203 
Nucleus contains a large nucleolus and some 
peripheral nucleoli. Yolk granules are not pres- 
ent in the cytoplasm. 
Cortical alveolar stage 
256.10 (3.08) 
207-316 
Cortical alveolar vesicles and oil droplets appear 
in the c 3 doplasm. Yolk granules are not yet pres- 
ent in the cytoplasm. Nucleus is central within 
the yolk 
Vitellogenesis 
729.31 (17.58) 
324-876 
Yolk granules appear between cortical alveolar 
vesicles. As vitellogenesis advances, yolk gran- 
ules fill the c 3 d;oplasm until they are in contact 
with the nucleus, which remains in a central 
position. 
Migratory nucleus 
939.31 (7.77) 
902-1008 
Yolk granules and oil droplets start to fuse. 
Nucleus migrates to one pole of the oocyte. 
Hydration 
1672.50 (4.77) 
1523-1750 
Yolk granules form a single mass. Nucleus is not 
present in the cytoplasm. 
(Colmenero et al., 2013). This specialized spermato- 
genesis also has been found in other deep-sea species 
of Neoceratiidae (Jespersen, 1984) and of Macruridae 
(Fernandez-Arcaya et al., 2013), in the shore clingfish 
{Lepadogaster lepadogaster) (Mattei and Mattei, 1978), 
in species of Blennidae (Lahnsteiner and Patzner, 
1990), in a species of Ophidion (Mattei et al., 1993), in 
the dusky jawfish (Opistognathus whitehursti) (Manni 
and Rasotto, 1997), and in species of Scorpaena (Munoz 
et al., 2002; Sabat et al., 2009), which also release their 
eggs in gelatinous substances. 
Fecundity 
Because of their particular reproduction behavior, 
which includes a high parental investment in the off- 
spring, white anglerfish are likely to spawn once a 
year, and the population dynamics of this species are 
expected to be highly sensitive to external biological 
and ecosystem factors (ICES"^). Spawning occurs in 
deep waters because mature white anglerfish have 
been described by Hislop et al. (2001) as migrating to 
deeper water before spawning. The same behavior is 
seen in yellow goosefish: adult fish migrate to deeper 
waters in response to seasonal changes in water tem- 
perature and gonadal maturation (Yoneda et al., 2002). 
ICES (International Council for the Exploration of the 
Sea). 2012. Report of the working group on the assess- 
ment of southern shelf stocks of hake, monk and megrim 
(WGHMM), 10-16 May 2012, ICES Headquaters, Copenha- 
gen, Denmark. ICES CM 2012/ACOM:11, 617 p. 
These vertical migrations into deeper waters where 
commercial fishing and scientific surveys cannot reach 
could be the reason that very few mature females were 
captured during our study — a trend that is common in 
other studies of Lophius species (Ofstad and Lauren- 
son®). Clearly, this low number of mature females will 
affect the estimation of such reproductive parameters 
as fecundity. 
Generally, deep-sea species have low fecundity and 
large egg sizes (Gage and Tyler, 1991; Herring, 2002). 
The white anglerfish has determinate fecundity with 
values between 661,647 to 885,214 oocytes — levels that 
are high in comparison with other deep-sea species that 
inhabit the same depth strata but that are similar to 
the mean potential fecundity of its Mediterranean con- 
generic, the black anglerfish (Colmenero et al., 2013). 
Fecundity values vary among populations as a result 
of adaptations to local environmental conditions, and 
they are related to abiotic factors, such as temperature 
and salinity (Nissling and Dahlman, 2010; Thorsen et 
al., 2010), and to biotic factors, such as food supply, 
population density, allocation of energy to reproduction, 
and fish size (Treasurer, 1981; Merrett, 1994; Nash et 
al., 2000). 
In this study, we were not able to determine cor- 
relations between fecundity and these factors because 
only 2 actively spawning females were collected. Eggs 
of white anglerfish have been reported to have a mean 
diameter of 2.72 mm (SD 0.08) (Colmenero et al., 
2015b), a size that is considered large for pelagic eggs, 
which typically range from 0.5 to 5.5 mm in diameter 
(Ahlstrom and Moser, 1980). Larger eggs have more 
