396 
Fishery Bulletin 111(4) 
Gonad maturity stages: □ I oil 
0 III □ IV b V 
A 
n = 103 123139 125 57 135 129 141 99 132130124 
^ ^ ^ V* ^ o* ^ <f° 
B 
0% M V h 1 M M M M U M h 1 
n = 105 107 79 73 46 85 59 95 104 87 97 93 
^ ^ ^ ^ ^ ^ o a ° 
Month 
Figure 3 
Monthly distributions of (A) males and (B) females in the 5 phases of gonad maturity of Black Ang- 
lerfish ( Lophius budegassa) collected from the northwestern Mediterranean Sea between June 2007 
and December 2010 and monthly changes in the mean gonadosomatic index (GSI) and hepatosomatic 
index (HSI) for (C) males and (D) females. On the basis of macroscopic examination, specimens were 
assigned to the following phases: immature (phase I), developing or regenerating (phase II), spawning 
capable (phase III), actively spawning (phase IV), and regressing (phase V). Error bars indicate ±1 
standard error of the mean. 
vesicles were found in the cytoplasm together with oo- 
cytes in the stage of primary growth with diameters 
that had increased notably (Fig. 5B). In phase III, yolk 
granule stages (Murua et al., 2003) were present along 
with the previous 2 types of oocytes. The oocytes in- 
creased in size as the yolk accumulated, and a wider 
oocyte diameter range distribution was observed dur- 
ing this phase (Fig. 50. In phase IV, oocytes were ob- 
served in different stages (primary growth, vitellogene- 
sis, migratory nucleus, and hydration). Two populations 
of oocytes were recognized in phase IV: a population of 
larger oocytes (defined as a clutch) and a population 
of smaller oocytes from which the clutch was recruited 
(Fig. 5D). In phase V, oocytes in the primary growth 
stage were found along with postovulatory follicles and 
atretic oocytes (Fig. 5E). 
The presence of oocytes in different developmental 
stages within the same cluster and the frequency dis- 
tribution of oocyte diameter along all maturity phases 
indicate that oocyte development in Black Anglerfish is 
group-synchronous. The existence of a gap that sepa- 
rates the yolked oocyte stock, the ones to be spawned 
during the current breeding season, from the unyolked 
oocytes, the ones to be spawned in the coming breeding 
season, together with the increase of the mean diam- 
eter of the advanced vitellogenic oocytes, indicates that 
annual fecundity is determinate. 
Significant differences in oocyte densities among 
