397 
Macchi et al.: Effects of skipped spawning on the reproductive potential of Merluccius hubbsi 
Table 1 
Number of samples and subsamples of specimens collected from the Patagonian stock of Argentine 
hake ( Merluccius hubbsi), as well as the number of ovaries collected for estimation of fecundity. 
Research surveys were carried out during the spawning peak (January) and the resting period 
(August) of this stock in the north Patagonian region of Argentina from 2005 through 2013. 
Year 
Total samples 
in January 
Female samples 
in January 
Female subsamples 
in January 
Female samples 
in August 
Ovaries 
for fecundity 
2005 
16250 
6810 
2322 
3228 
178 
2006 
8500 
4022 
2546 
111 
2007 
8804 
5634 
2015 
4371 
78 
2008 
13,881 
7045 
1954 
110 
2009 
15,813 
7970 
1969 
101 
2010 
19,683 
9485 
2037 
105 
2011 
13,487 
6420 
1959 
5577 
731 
2012 
19,362 
9533 
3448 
3030 
82 
2013 
31,956 
14,155 
3361 
7392 
97 
al., 2016). These individuals were located mostly on the 
periphery of the spawning area at depths close to 100 
m, and they were mainly young adult females. 
We report on our continued study of skipped spawn- 
ing in Argentine hake. The main purpose of the re- 
search described in our study was to establish how 
this phenomenon affects the reproductive potential of 
the Patagonian stock of this species. We constructed 
length- and age-based maturity models by using 2 
interpretations of the maturity cycle: 1) females that 
had skipped spawning were classified as mature (tra- 
ditional interpretation) and 2) mature females that 
had not spawned during the reproductive season were 
classified as functionally immature (revised interpreta- 
tion). We also examined the relationship between the 
demographic composition of the stock and the incidence 
of skipped spawning. We estimated the proportion of 
the total reproductive potential that was reduced as 
a result of skipped spawning by analyzing data from 
research surveys performed during peak spawning of 
the Patagonian stock of Argentine hake. 
Materials and methods 
Sample collection and laboratory processing 
Most of our samples were collected in the summer dur- 
ing 9 research surveys conducted by the Institute Na- 
tional de Investigation y Desarrollo Pesquero (INIDEP) 
in the north Patagonian area off Argentina between 
2005 and 2013 (Table 1). These surveys were performed 
during the peak spawning time for the Patagonian 
stock of Argentine hake (January) in the area of repro- 
duction, and in the main nursery ground for young-of- 
the-year individuals in the San Jorge Gulf. Trawling 
during these surveys was conducted at depths between 
50 and 120 m along transects regularly separated by 
approximately 37 km (20 nmi) and oriented perpendic- 
ularly to the coastline (Fig. 1). We also had data from 
samples of females collected during 5 surveys carried 
out in the same area (43-47°S and 61-67°W) in August 
(austral winter) when the Patagonian stock of Argen- 
tine hake was in a resting reproductive stage (Table 
1). In these 5 surveys, 50-90 stations were sampled by 
using a stratified random design for the entire study 
area, at depths between 50 and 200 m. The bottom 
trawl used for all surveys had a mouth width of ap- 
proximately 20 m, a height of 4 m, and a net with a 
20-mm mesh liner in the codend. 
After weighing the catch of Argentine hake, a ran- 
dom sample was taken to determine sex, and the total 
length (TL, in centimeters) was recorded for each fish. 
Moreover, the maturity of each specimen was assessed 
macroscopically on the basis of a 5-stage maturity 
key: 1) immature, 2) developing, 3) spawning, 4) post- 
spawning or spent, and 5) resting or recovering. This 
maturity scale was previously validated for females by 
histological analysis of the ovaries and was described 
in Macchi et al. (2016). For this reason, to estimate 
length and age at maturity (L 50 and A 50 , respectively), 
we used only macroscopic information. To estimate age 
composition, sagittal otoliths were collected from ran- 
dom subsamples of female Argentine hake collected 
from different sampling stations during January sur- 
veys (Table 1). Ages, based on analysis of these otoliths, 
were determined by using a method described by Renzi 
and Perez (1992). 
To estimate models of batch fecundity versus TL and 
batch fecundity versus age for the Patagonian stock, we 
collected females classified as spawning (with hydrated 
oocytes) from different sampling stations, and fixed the 
ovaries in 10% neutral-buffered formalin for histologi- 
cal analysis (Table 1). The ovaries were weighed to the 
nearest 0.1 g to obtain gonad weight, and a portion 
(approximately 2.0 g) of each gonad was then removed, 
