40 
Fishery Bulletin 1 14(1) 
Table 2 
Results from an analysis of covariance between sexes 
of red flying squid ( Ommastrephes bartramii) in the 
relationships between age and the following variables: 
mantle length (ML), body weight (BW), and upper ros- 
tral length (URL). No differences between sexes were 
significant. 
Measurements 
df 
F 
P 
ML 
107 
0.125 
0.725 
BW 
199 
0.065 
0.806 
URL 
151 
1.974 
0.166 
ML and 11.33 g/d for BW within 301-350 d (Table 
1; Fig. 4, A and B), and the maximum G was 0.31 
for ML within 301-350 d and 0.97 for BW within 
251-300 d. In males, maximum DGR occurred within 
251-300 d for ML (0.83 mm/d) and then decreased, 
and maximum G also occurred during within 251-300 
d for both ML (0.28) and BW (0.89) (Table 1, Fig. 4, 
A and B). 
On the basis of results of the ANCOVA test, there 
was no significant difference in ML, BW, and URL be- 
tween females and males (P>0.05) (Table 2). Therefore, 
we used the pooled data to analyze the relationship 
between ML, BW, URL, and age. Growth curves of 
ML-age and BW-age relationships were fitted with 
an exponential model, and the URL-age relationship 
provided the best fit with a linear model (Fig. 4, C-E) 
because it represented the best fit to the data (Table 3). 
These relationships were calculated with the following 
equations: 
ML-age relationship: ML = 148.47e 0 0028age (coeffi- 
cient of determination [r 2 ]=0.980, n=211, P<0.01) 
BW-age relationship: BW = 83.80e° 009age (r 2 =0.914, 
n=211, P<0.01) 
URL-age relationship: URL = 0.0141age + 3.6816 
(r 2 =0.460, ti= 211, PcO.Ol) 
Discussion 
The beak has been used to estimate age for a few 
neritic molluscan species (e.g., the common octopus, 
Perales-Raya et al., 2014; Octopus maya, Barcenas et 
al., 2014). On the basis of the results of our study, we 
can see that the microstructure of the beak in red fly- 
ing squid is similar to that in different cephalopods, 
as was reported in a previous study (Perales-Raya et 
al., 2010). Although the rostrum in squids seems to 
account for a much larger proportion of the crest than 
it does in octopuses, RSS increments are smaller in 
squid than in octopuses, nearly 12 pm in this study 
compared with roughly 20 pm for common octopus 
(Raya and Hernandez-Gonzalez, 1998) and with 15-30 
pm after 50 increments reported by Perales-Raya et 
al. (2010). In this study, we used only reflected light 
to observe the increments clearly, as opposed to the 
use of violet or ultraviolet light by Perales-Raya et al. 
(2010). It is easy to distinguish RSS increments at low 
magnification with reflected light, 
but this method should be used with 
caution because it is easy to con- 
fuse “first-order” and “second-order” 
increments, as it is with statoliths 
(Arkhipkin and Shcherbich, 2012). 
Check rings were also found in this 
study, and those rings may have 
resulted from stressful conditions, 
such as spawning (Perales-Raya et 
al., 2014). The microstructure of 
statoliths also displays check rings 
(Chen et al., 2013). 
This study is one of the first that 
has provided estimated ages for oce- 
anic species of ommasterphid squid 
on the basis of beak microstructure. 
Cephalopods are typically short-lived 
invertebrates, and the lifespan of red 
flying squid was estimated to aver- 
age about 1 year in previous reports 
(Bigelow and Landgraph, 1993; Yat- 
su et al., 1997; Chen and Chiu, 2003; 
Chen et al., 2011). All the squid ana- 
lyzed in this study were less than 1 
year in age, and the results of this 
study are consistent with the results 
of previous studies where ages were 
Table 3 
Estimated model parameters and Akaike’s information criterion (AIC) val- 
ues of the relationship between age and the following variables: mantle 
length [ML], body weight (BW), and upper rostrum length (URL) for red 
flying squid (Ommastrephes bartramii). Underlined values are the lowest 
AIC values chosen with the best model. Linear=linear function: y=a+bx\ 
power=power function: y=ax b ; exponential=exponential function: y =ae bx ; 
logarithmic=logarithmic function: y- 
criterion. 
=aln(x)+6; AIC 
= Akaike’s 
information 
Body variables 
Age (d) 
Model 
a 
b 
AIC 
ML 
Linear 
0.763 
111.766 
846.971 
Power 
12.773 
0.573 
924.242 
Exponential 
147.200 
0.003 
755.171 
Logarithm 
-500.730 
145.350 
1020.454 
BW 
Linear 
5.389 
-500.970 
2008.414 
Power 
0.008 
2.102 
1918.870 
Exponential 
74.541 
0.010 
1850.317 
Logarithm 
-4704.3 
1003.1 
2091.505 
URL 
Linear 
0.014 
3.682 
-93.550 
Power 
0.682 
0.427 
-91.991 
Exponential 
4.211 
0.002 
-93.228 
Logarithm 
-7.775 
2.711 
-89.493 
