54 
Fishery Bulletin 116(1) 
Table 2 
Results of analysis of variance between sexes for stan¬ 
dardized ( s ) gladius morphometric variables of jumbo 
squid (Dosidicus gigas ) sampled in 2009, 2013, and 
2014 off the Peruvian exclusive economic zone (PE) and 
in offshore waters of the central eastern Pacific (CEP). 
The morphometric variables are conus length (CL), 
maximum width of conus (CW), proostracum length 
(PL), maximum width of prostracum (PW), length from 
anterior tip of conus to the widest point of proostracum 
(PWL), length from anterior tip of conus to proximal 
end of lateral plates (LPL), and width between 2 anteri¬ 
or apices of lateral plates (LPW). n=number of samples; 
F=variance between the means of female and male val¬ 
ues; ns=nonsignificant, probability (P)>0.05; *=P<0.05; 
**=P<0.01 
PE CEP 
Variable 
F 
P 
F 
P 
n 
282 
175 
CL S 
3.72 
ns 
38.67 
** 
CW S 
2.40 
ns 
27.06 
** 
PL S 
8.21 
** 
281.11 
** 
PW S 
5.93 
* 
89.90 
** 
PWL S 
26.29 
** 
57.87 
** 
LPL S 
3.07 
ns 
78.39 
** 
LPW S 
4.34 
* 
60.13 
** 
LPL S of PE specimens were not different for the sexes 
(Table 2). Meanwhile, the SDA results showed that the 
correct cross-validated classification rates reached from 
62.4 % to 94.3 % for the region off PE and within the 
CEP, respectively (Table 3). The results may indicate 
a significant difference between the sexes within each 
population. 
Geographic variations 
For all individuals, the PCA of the morphometric fea¬ 
tures of squid gladii retained two principal components 
(PCI and PC2), having eigenvalues greater than 1 and 
accounted for 62.40 % and 14.81 % of the total vari¬ 
ance, respectively. The main variables counting for 
variation in PCI were CL S , PL S , PW S , PWL S , LPL S , 
and LPW S . Variation of PC2 was mainly influenced by 
CW S . The SDA performed on all samples identified four 
valid gladius morphometric features (CLs, CW S , PL S 
and PW S ) that served as discriminatory variables for 
the three geographic populations (Table 4). The first 
canonical function explained 83.9% of the total vari¬ 
ance. Although there was considerable overlap, the fi¬ 
nal correct cross-validated classification rates among 
the geographic populations reached 80.0% (off the 
CRD), 74.8% (off the PE) and 84.0% (within the CEP), 
respectively (Table 5A). 
The PCA performed on data sets for females detected 
only one principal component with eigenvalues greater 
Table 3 
The percentages of cross-validated classification from 
stepwise discriminant analysis for each sex of 2 geo¬ 
graphic populations of jumbo squid (Dosidicus gigas) 
sampled in 2013 and 2014 off the Peruvian exclusive 
economic zone (PE) and in offshore waters of the central 
eastern Pacific (CEP). 
PE CEP 
Female Male Female Male 
Female 62.0% 38.0% 96.1% 3.9% 
Male 36.7% 63.3% 8.2% 91.8% 
Total 62.4% 94.3% 
P <0.001 <0.001 
than 1 and explaining 65.30% of the total variance. 
All morphometric features showed high contributions 
to the principal component analysis. The SDA selected 
CL S , CW S , PL S , and PW S as suitable variables to dis¬ 
tinguish female D. gigas from the three regions, with a 
misclassification rate of 16.8% (Tables 4 and 5B). 
A total of 340 statoliths from the three sites were 
satisfactorily prepared for age determination. In all 
three population units, values of DGR for PL were 
larger than CL during all studied periods for each sex 
(Friedman test, P<0.01, Table 6), although small sam¬ 
ple sizes may have influenced the reliability of calcu¬ 
lated growth rates in some age groups. 
For each geographic population, the maximum DGR 
in CL was found from 201 to 225 days of age for female 
D. gigas (Table 6). Although the maximum DGR in PL 
occurred at different periods, the value for off the CRD 
(1.44 mm/d, 201-225 days) and off the PE (1.12 mm/d, 
201-225 days) were larger but occurred later than the 
CEP value (1.11 mm/d, 176-200 days). For males, the 
maximum DGR in CL (0.41 mm/d) was reached from 
201to 225 days of age for PE, wheras in the CEP the 
maximum is smaller (0.34 mm/d) and it is reached be¬ 
fore, at 176-200 days. In contrast, the maximum DGR 
in PL was observed at 201-225 and 176-200 days for 
males off the PE and within the CEP (Table 6). 
Discussion 
Gladius structure 
In D. gigas, a strong correlation was found between 
GL and ML in each geographic population. This finding 
indicates that the gladius can be considered a hard tis¬ 
sue that supports the mantle and internal organs. Sim¬ 
ilar results were reported for other ommastrephids, II- 
lex illecebrosus (Perez et ah, 1996) and Ommastrephes 
bartramii (Kato et al., 2016). Also, GL may be a more 
reliable measurement than ML when individuals are 
