64 
Fishery Bulletin 1 15(1) 
Figure 2 
Histological sections from ovaries of female white ang- 
lerfish (Lophius piscatorius) in 3 phases of maturity: 
(A) immature, (B) spawning capable, and (C) actively 
spawning. Ov=ovigerous membrane, Nov=nonovigerous 
membrane, n=nucleus, Pg=primary growth stage, 
Vt=vitellogenesis stage, Od=oil droplet, Yv=yolk vesi- 
cle, Mm^mucus matrix. Scale bars=100 pm. 
cm TL. The lengths at which 25% and 75% of fish at- 
tained maturity were 43.5 and 53.4 cm TL for males, 
48.6 and 71.1 cm TL for females, and 44.7 and 58 cm 
TL for the sexes combined. 
Oocyte development and fecundity 
Oocytes in different developmental stages were found 
in each maturity phase. They were organized in clus- 
ters where a gradient in the size of the oocyte was ob- 
served. A group of oocytes differentiated from others as 
the ovaries developed, indicating that white anglerfish 
has group-synchronous oocyte development and can be 
considered to have determinate fecundity (Fig. 7). Ova- 
ries at each maturity phase contained primary oogonia- 
and perinucleolar-stage oocytes. Chromatin nucleolar 
were difficult to find and were present only in imma- 
ture phase. Females at the cortical alveolar stage were 
not found in our samples. Vitellogenic and hydrated 
oocytes were located in females capable of spawning. 
Oocyte diameters at each stage of oocyte development 
are shown in Table 2. 
Batch fecundity ranged from 661,647 to 885,214 
oocytes from 2 females that measured 76 and 105 cm 
TL, 6331 and 16,178 g TW, and 5182 and 13,330 g 
GW, respectively. Relative batch fecundity ranged from 
66 to 128 oocytes/g GW (average of 97 oocytes/g GW 
[standard deviation, SD 43] ). Potential fecundity values 
moved from 54,717 to 104,506 oocytes/kg TW with a 
mean of 79,612 oocytes/kg TW (SD 35,206). 
Discussion 
Relevance of reproductive traits for sustainable 
management 
Fishing activity during spawning seasons may affect 
population parameters, specifically composition of the 
size distribution, mortality rate, sexual structure of the 
population, size at maturity, and changes in the spawn- 
ing season. These parameters, in turn, can increase the 
risk of over-exploitation of a stock. 
Fishing during spawning periods may result in tar- 
geting a specific size class of the population and thus 
increasing the chance of catching the older (and larger) 
age classes and making the stock vulnerable to repro- 
ductive collapse (van Overzee and Rijnsdorp, 2015). 
Because spawning is generally limited to specific ar- 
eas and times (Cushing, 1990), the conservation of re- 
sources can be enhanced by limiting fishing activity in 
a spatiotemporal frame. Furthermore, fishing pressure 
has been documented to have reduced initial size at 
maturity — an issue that is a concern particularly for 
late-maturing species (Stewart et al., 2010). If size of 
capture is below the size at first maturity, there is a 
genuine risk of recruitment overfishing. Therefore, 
knowledge of the spawning season and the size at ma- 
turity can help managers establish closed seasons and 
prevent fishing at this vulnerable time in the life cycle 
