Macchi et al.: Effects of skipped spawning on the reproductive potential of Merluccius hubbsi 
403 
250 
S' 
O 200 
c n 
0) 
E 150 
o 100 
0 
■O 
1 50 
z 
0 
■ Females in resting stage as mature 
Females in resting stage as functionally immature 
1 2 3 4 5 6 7 8 9 10 11 12 13 14 
Age (years) 
Figure 4 
Age-frequency distributions obtained for adult female Ar- 
gentine hake ( Merluccius hubbsi) collected from the Patago- 
nian stock off Argentina during January 2005-2013, aver- 
aged across years. The black area represents the fraction 
of females that would skip spawning during the spawning 
peak of the stock. The age-at-maturity model was applied 
in 2 ways to create the 2 overlapping areas: females in the 
resting stage were considered mature (black) or functionally 
immature (gray). 
length classes during the spawning peak in Janu- 
ary varied annually during the period 2005-2013 
(Fig. 5). During most years, the egg production de- 
pended on females larger than 50 cm TL, except 
in 2005 and 2006, when the abundance of smaller 
adult individuals was particularly high (Fig. 3). Af- 
ter considering the incidence of SS in the estimate 
of egg production by length class, it was evident 
that the SS phenomenon affected mainly females 
smaller than 50 cm TL (Fig. 5). The reduction in egg 
production of one batch ranged from 2.70% to 6.80% 
when we compared egg production by length class 
(Fig. 6). The lowest value in the reduction of egg 
production during the period analyzed was observed 
in 2012, and it was coincident with a low propor- 
tion of females that had skipped spawning (Fig. 3). 
The analysis of egg production by age class, af- 
ter both interpretations of maturity were applied, 
confirmed that SS is observed mainly in young fe- 
males (Fig. 7). In this case, the reduction in egg 
production of one batch on account of SS ranged 
from 3.56% to 12.12%. As found with the compari- 
son by length class, 2012 was the year with the 
lowest egg production by age class (Fig. 6). 
2005 2006 
10 20 30 40 50 60 70 80 90 10 20 30 40 50 60 70 80 90 
2007 
9 
10 20 30 40 50 60 70 80 90 
10 20 30 40 50 60 70 80 90 10 20 30 40 50 60 70 80 90 10 20 30 40 50 60 70 80 90 
/ 
20 30 40 50 60 70 80 90 
Total length (cm) 
2012 
10 20 30 40 50 60 70 80 90 
Total length (cm) 
2013 
10 20 30 40 50 60 70 80 90 
Total length (cm) 
Figure 5 
Egg production by length class in one spawning event, estimated for female Argentine hake (Merluccius hubbsi) collected 
from the Patagonian stock off Argentina in January during the spawning peak of 2005-2013. The black area represents the 
fraction by which the egg production was reduced by females that would skip spawning (SS), and the gray area indicates 
the actual egg production. 
