Gong et ai.: Geographic variations in the distribution Dosidicus gigas 
53 
Table 1 
Summary information, including mean dorsal mantle length (ML) and body weight (BW) with standard deviations (SDs), for 
jumbo squid (Dosidicus gigas ) sampled in 2009, 2013, and 2014 off the Costa Rica Dome (CRD), off the Peruvian exclusive 
economic zone (PE), and in offshore waters of the central eastern Pacific (CEP) to examine the use of morphological features 
to distinguish between populations in different geographic zones. n=number of squid in a sample 
ML (cm) BW (g) 
Geographic 
population 
n (F, M) 
Sampling 
date 
Coordinates 
Maturity 
stage 
Maxi¬ 
mum 
Mini¬ 
mum 
Mean 
SD 
Maxi¬ 
mum 
Mini¬ 
mum 
Mean 
SD 
CRD 
105 
(89, 16) 
Jul. to 
Aug. 2009 
91°48 - 99°30'W 
6°36'- 9°30'N 
I-IV 
40.9 
21.8 
29.5 
3.1 
1907.5 
252.6 
737.2 
256.9 
PE 
32 
(27, 5) 
Sep. to 
Oct. 2009 
82°06'- 84°29'W 
10°21- 11°17'S 
I-III 
44.7 
26.4 
32.7 
4.6 
2928.7 
490.0 
1088.2 
555.4 
179 
(116,63) 
Jul. to 
Oct. 2013 
79°57- 83°24'W 
10°54'- 15°09'S 
I-IV 
39.6 
21.8 
26.8 
4.3 
1647.0 
278.0 
548.8 
379.8 
71 
(38, 33) 
Feb. to 
Sep. 2014 
74°57 - 83°13'W 
10°26'-22°38'S 
I-IV 
48.5 
19.1 
28.1 
7.3 
3361.0 
177.0 
767.9 
721.4 
CEP 
121 
(57, 64) 
Apr. to 
Jun.2013 
114 o 59'-119°00'W 
0°28'N-1°00'S 
I-IV 
37.2 
22.2 
29.2 
3.7 
1523.0 
291.0 
746.7 
300.7 
54 
(45, 9) 
Apr. to 
May. 2014 
116°00- 117°19'W I-III 
0°42'- 0°58'N 
41.2 
27.5 
33.0 
3.0 
1849.0 
608.0 
1059.8 
300.9 
Principal component analysis (PCA) was used to 
determine the main morphometric variables among 
three population units by reducing the multidimen¬ 
sional data. SDA was performed on the results of PCA 
to identify the variables that would distinguish the 
geographic populations and calculate the classification 
rates. 
Moreover, to remove the potential impacts of the 
disproportionate number of female D. gigas and differ¬ 
ent sex ratios for the three sites, PCA and SDA were 
repeated with female data only as an independent data 
set to evaluate the geographic divergence of females. 
The analyses of growth rates were performed on un¬ 
transformed morphometric and age data. The absolute 
daily growth rate (DGR, mm/day) was calculated for 
each 25-day interval with the following equation (For¬ 
sythe and Van Heukelem, 1987): 
DGR = -2- ~ Ll , (3) 
t 2 —1 1 
where L = one of the morphometric variables of the 
gladius; 
Li and L 2 - the observed values (mm) at the be¬ 
ginning (fj) and the end (t 2 ) of each interval 
of time (day). 
Multiple comparison was examined by using ANOVA 
with post-hoc Tukey’s honestly significant difference 
(HSD) test. For nonnormal and ordinal data, a matched 
comparison with the Friedman test was applied. A P 
value of <0.05 was considered significant for all statis¬ 
tical tests, and statistical analyses were carried out by 
SPSS Statistics, 1 vers. 19.0 (IBM Corp., Armonk, NY). 
Results 
Gladius structure 
Morphometric variables of the three geographic popu¬ 
lations are presented in the Supplementary Table. 
Regression analysis performed on the GL and ML 
showed strong correlations within the three geograph¬ 
ic populations (CRD: r= 0.95, ML=1.005GL+1.267; 
PE: r= 0.98, ML=0.94GL + 0.99; CEP: r=0.99, 
ML=1.03GL-0.63). As main morphological parts of the 
gladius, the ratio of CL to PL (CL/PL) showed signifi¬ 
cant differences (ANOVA, P<0.05, F 2i 558 =87.30) among 
regions. The CL/PL values for squid off the CRD (0.22 
±0.02) were lower than those off the PE (0.24 ±0.02) 
and CEP squid (0.26 ±0.02). In addition, the CL 
showed significant positive relationships with FW (CR: 
r=0.77; PE: r=0.90; CEP: r=0.70) and FL (CR: r=0.82; 
PE: r=0.89; CEP: r=0.72). 
Sexual dimorphism 
When comparing morphometric characteristics between 
females and males, we found that only CL S , CW S and 
1 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. 
