62 
Fishery Bulletin 115(1) 
Figure 1 
Map of the northwestern Mediterranean Sea showing the study area where 
white anglerfish (Lophius piscatorius) were collected from fishing grounds 
off the Catalan coast between June 2007 and December 2010. 
collected monthly aboard commercial fishing ves- 
sels that were trawling at depths of 12-836 m. Fish 
were sampled from 467 stations located in the fish- 
ing grounds off the Catalan coast in the northwestern 
Mediterranean Sea from 40°5.980'N to 43°39.310'N 
and from 0°32.922'E to 3°35.718'E (Fig. 1). For each 
individual, TL was measured to the nearest centimeter, 
total weight (TW) and gutted weight (GW) were mea- 
sured to the nearest gram, and gonad weight (GNW) 
and liver weight (LW) were measured to the nearest 
0.01 g. The sex of all fish was determined and assigned 
macroscopically to a gonadal stage on the basis of a 
scale of 5 maturity phases proposed by Colmenero et 
al. (2013): immature (phase I), developing or regener- 
ating (phase II), spawning capable (phase III), actively 
spawning (phase IV), and regressing (phase V). 
Fish that were too small (<20 cm TL) for their sex 
to be determined or for assignment to a gonadal phase 
were classified as indeterminate. Macroscopic gonadal 
stage was validated histologically, according to the 
most advanced cell within the gonad (West, 1990). 
Gonads were fixed in 10% buffered formalin solution, 
dehydrated in ascending solutions of alcohols and em- 
bedded in a methacrylate polymer resin, sectioned at 
a thickness of 4 pm with a manual microtome Leica 
Reichert-Jung 2040^ (Leica Microsystems, Wetzlar, Ger- 
many), stained with Lee’s stain (methylene blue and 
basic fuchsin), and mounted in a synthetic resin of di- 
butyl phthalate xylene on microscope slides. Gonads 
were classified according to their size and color and the 
presence or absence of specific inclusions (oil droplets, 
^ Mention of trade names or commercial companies is for iden- 
tification purposes only and does not imply endorsement by 
the National Marine Fisheries Service, NOAA. 
yolk, postovulatory follicles, or sperm), as well as the 
type of oocytes (Wallace and Selman, 1981). 
Reproductive biology 
The spawning season was estimated by analyzing the 
monthly variation in the percentage of maturity phas- 
es and the changes in gonadosomatic index (GSI) and 
hepatosomatic index (HSI) for mature fish of each sex 
(Afonso-Dias and Hislop, 1996; Colmenero et al., 2013). 
Because indeterminate individuals (n=27) were not 
considered, 251 males and 278 females were used to 
determine both indices, which were calculated accord- 
ing to Yoneda et al. (2001) as 
and 
GSI = (GNW / GW) X 100 
HSI = (LW / GW) X 100. 
( 1 ) 
( 2 ) 
The lengths at which 25%, 50%, and 75% of sampled 
fish reached sexual maturity were estimated by fitting 
the proportion of sexually mature males and females 
(phase III, phase IV, or phase V) and for both sexes 
combined to the logistic equation (Colmenero et al., 
2013): 
P = 100 / (1 + exp [a -I- bTL]), (3) 
where P = the percentage of mature individuals as a 
function of size class (measured in TL); 
and 
a and b are specific parameters that can change 
during the life cycle. 
A logarithmic transformation was applied to this equa- 
tion to calculate the parameters a and b by means of 
linear regression. 
